From  the  collection  of  the 


7      n 

z        m 

PreTinger 

V  lilvna 


ibrary 


San  Francisco,  California 
2006 


THE    ROMANCE    OF    MODERN 
ASTRONOMY 


Of    THE 

UN!VERS!TV 

^^UFOH*^* 


HALLEY'S  COMET,  1910 

To  the  ordinary  observer  this  comet  has  proved  a  failure  as  a  popular  spectacle. 
But   as   seen    through   a   powerful  telescope  it  has  been  far  from  disappointing. 
This  illustration  has  been  made  from  a  drawing  at  Greenwich  Observatory.     It 
represents  the  aigrette  or  fan  spreading  forward  from  the  nucleus  in  the  direct 
of  the  comet's  motion. 


THE  ROMANCE  OF 
MODERN  ASTRONOMY 

DESCRIBING    IN    SIMPLE   BUT   EXACT 

LANGUAGE    THE    WONDERS    OF   THE 

HEAVENS 


BY 


HECTOR    MACPHERSON,   JUNR. 

MEMBRK  DE   LA  SOCIKTlt  ASTKONOMIQUE  UK  FRANCE  ET 

LA   SOCIETY   BELGE   D'ASTRONOMIE 
MEMBER  OF   THE  ASTRONOMICAL  INSTITUTION   OF  EDINBURGH 

AUTHOR  or  "ASTRONOMERS  OF  TO-DAY,"  "A  CENTURY'S  PROGRESS 

IN   ASTRONOMY,"   "THROUGH   THE   DEPTHS  OF   SPACE" 


WITH  THIRTY-NINE  ILLUSTRATIONS  6*  DIAGRAMS 


OfTHC 

UNIVER8ITV 

Of 


LONDON 
SEELEY  AND  CO.  LIMITED 

38  GREAT  RUSSELL  STREET 
1911 


UNIFORM   WITH  THIS  VOLUME 

THE    LIBRARY    OF    ROMANCE 

Extra  Crown  8vt.    With  many  illuttrations.    5*.  each 
"Splendid  volumes."— The  Outlook. 

"Each  volume  treats  Its  allotted  theme  with  accuracy, 
but  at  the  same  time  with  a  charm  that  will  commend 
itself  to  readers  of  all  ages.  The  root  idea  is  excellent, 
end  it  is  excellently  carried  out,  with  full  illustrations  and 
very  prettily  designed  covers."— The  Dally  Telegraph. 

By  Prof.  G.  F.  SCOTT  ELLIOT,   M.A.,  B.Sc. 
THE  ROMANCE  OF  SAVAGE  LIFE 
THE  ROMANCE  OF  PLANT  LIFE 
THE   ROMANCE  OF   EARLY   BRITISH   LIFE 

;  .  .  3y  EDWARD  GILLIAT,   M.A. 
'    THE   ROMANCE  OF   MODERN   SIEGES 

By  JOHN   LEA,   M.A. 
TH^.  ROMANCE  OF   BIRD  LIFE 

By  JOHN  LEA,  M.A.,  &  H.  COUPIN,  D.Sc. 

THE  ROMANCE  OF  ANIMAL  ARTS  AND  CRAFTS 

By  SIDNEY  WRIGHT 
THE  ROMANCE  OF  THE  WORLD'S   FISHERIES 

By  the  RCT.  J.  C.  LAMBERT,  M.A.,  D.D. 
THE  ROMANCE  OF  MISSIONARY    HEROISM 

By  G.  FIRTH  SCOTT 
IHE  ROMANCE  OF  POLAR  EXPLORATION 

By  ARCHIBALD  WILLIAMS,  B.A.  (Oxon.),  F.R.G.S, 
THE  ROMANCE  OF   EARLY   EXPLORATION 
THE  ROMANCE  OF  MODERN   EXPLORATION 
THE  ROMANCE  OF  MODERN  MECHANISM 
THE  ROMANCE  OF  MODERN   INVENTION 
THE  ROMANCE  OF  MODERN   ENGINEERING 
THE  ROMANCE  OF  MODERN   LOCOMOTION 
THE   ROMANCE  OF  MODERN   MINING 

By  CHARLES  R.  GIBSON,  F.R.S.E. 
THE  ROMANCE   OF   MODERN   PHOTOGRAPHY 
THE  ROMANCE  OF  MODERN   ELECTRICITY 
THE  ROMANCE   OF   MODERN   MANUFACTURE 

By  EDMUND  SELOUS 

THE  ROMANCE  OF  THE  ANIMAL  WORLD 
THE  ROMANCE  OF  INSECT  LIFE 

By  AGNES  GIBERNE 
THE  ROMANCE  OF  THE  MIGHTY  DEEP 

By  E.  S.  GREW,  M.A. 
THE  ROMANCE  OF   MODERN  GEOLOGY 

By  J.  C.  PHILIP,  D.Sc.,  Ph.D. 
THE  ROMANCE  OF  MODERN  CHEMISTRY 

By  HECTOR  MACPHERSON,  Junr. 
THE  ROMANCE  OF  MODERN  ASTRONOMY 

»  By  E,  KEBLE  CHATTERTON,  B.A.  (Oxon) 

THE  ROMANCE  OF  THE  SHIP 


PREFACE 

IN  the  preparation  of  this  volume  the  writer  has  re- 
ceived invaluable  assistance  from  several  well-known 
astronomers.     His  special  thanks  are  due  to  Mr. 
J.  E.  Gore  and  Mr.  E.  W.  Maunder  for  their  kindness 
in  reading  over  and  correcting  the  proof-sheets,  and  for 
their   useful    suggestions ;    to  Professor   Percival   Lowell 
for  the  two  views  of  Mars  and  for  the  photograph  of 
Saturn ;   and  to  Professor   Max  Wolf  for  the  beautiful 
photographs  of  stars  and  nebulae  which...  are  reproduced 
here  by  his  kind  permission. 

Finally,  the  writer  has  to  mention  the  kindness  of 
Professor^Schiaparelli  for  furnishing  one  of  his  classical 
drawings  of  Mars,  and  for  permission  to  reproduce  it 
in  this  book.  Since  that  permission  was  granted,  Pro- 
fessor Schiaparelli's  death  has  bereft  astronomy  of  an 
illustrious  leader. 

July  IplO. 


CONTENTS 

CHAPTER    I 

PAGE 

OUR  PLACE  IN  THE  UNIVERSE 17 

CHAPTER   II 

EFFECTS  OF  THE  EARTH'S  MOTIONS      .         .         .        .26 

CHAPTER   III 

THE  ORB  OF  NIGHT     .  .  .37 

CHAPTEK   IV 
THE  FOUNTAIN  OF  LIGHT 48 

CHAPTER   V 
THE  SUN'S  FAMILY  OF  WORLDS 60 

CHAPTER   VI 

MERCURY,  THE  "  SPARKLING  ONE  "  .        .         .69 

CHAPTER   VII 
THE  EVENING  STAR 76 

CHAPTER   VIII 

MARS,  THE  RED  PLANET 83 

11 


CONTENTS 

CHAPTER    IX 

PAGE 

THE  ASTEROIDS .98 

CHAPTER   X 
JUPITER,  THE  GIANT  PLANET 106 

CHAPTER   XI 
SATURN,  THE  RINGED  WORLD 115 

CHAPTER   XII 

THE  BOUNDARIES  OF  THE  SOLAR  SYSTEM      .        .         .123 

CHAPTER  XIII 
THE  SUN'S  FAMILY  OF  COMETS 132 

CHAPTER   XIV 

THE  MESSENGERS  OF  SPACE          .  .     141 

CHAPTER   XV 

THE  NATURE  OF  COMETS 150 

CHAPTER   XVI 
THE  SHOOTING  STARS 159 

CHAPTER  XVII 

ECLIPSES  AND  TRANSITS 169 

CHAPTER   XVIII 

THE  SUNS  OF  SPACE 182 

12 


CONTENTS 

CHAPTER   XIX 

PAGE 

THE  REVELATIONS  OF  STARLIGHT 191 

CHAPTER  XX 

SYSTEMS  OF  STARS 201 

CHAPTER   XXI 

THE  MOTIONS  OF  THE  STARS 208 

CHAPTER  XXII 
THE  FIRE  MIST  ........     214 

CHAPTER   XXIII 
THE  GALAXY 219 

CHAPTER   XXIY 
THE  ORIGIN  OF  THE  UNIVERSE 226 

CHAPTER   XXV 
THE  ROMANCE  OF  THE  TIDES 236 

CHAPTER  XXYI 

LIGHT  AND  ITS  MYSTERIES    .  .  245 

CHAPTER  XXVII 
How  TO  KNOW  THE  STARS  .  .  .     251 

CHAPTER   XXVIII 

TELESCOPES  AND  OBSERVATORIES 261 

13 


CONTENTS 

CHAPTER  XXIX 

PAGE 

THE    ROMANCE    OF    DISCOVERY:    THE    EARLY    ASTRO- 
NOMERS         ........     273 

CHAPTER  XXX 
THE  ROMANCE  or  DISCOVERY  :  GALILEO  AND  KEPLER  .     283 

CHAPTER   XXXI 

NEWTON  AND  HIS  SUCCESSORS 295 

CHAPTER  XXXII 
THE  CONQUEST  OF  THE  STARS      .         .         .         .        .312 

CHAPTER   XXXIII 
A  FINAL  SURVEY  319 


14 


LIST    OF    ILLUSTRATIONS 

PAGE 

H ALLEY'S  COMET,  1910          .         .         .         .         Frontispiece 

THE  AURORA  BOUEALIS 32 

THE  NEW  MOON  AND  THE  SETTING  SUN        .         .         .38 

THE  MOON 44 

PHOTOGRAPH  OF  A  SUNSPOT 50 

THE  VARYING  FORCE  OF  GRAVITY  ON  THE  DIFFERENT 

PLANETS        .  .  64 

THE  PLANET  MARS 84 

THE  PLANET  JUPITER 102 

SATURN,  THE  PVINGED  WORLD 112 

How  SATURN  WOULD  APPEAR  FROM  ITS  NEAREST 

SATELLITE 118 

UNFOUNDED  FEAR  OF  THE  CHINESE  AT  THE  GREAT 

COMET  OF  JANUARY  1910 128 

DONATI'S  COMET,  1858 134 

MOREHOUSE'S  COMET,  1908 150 

A  SHOWER  OF  METEORS 156 

A  FIREBALL  OR  BOLIDE        .         .         .         .         .         .160 

THE  ZODIACAL  LIGHT  .  .  .  .  .  .  .168 

ECLIPSE  OF  THE  MOON 170 

ECLIPSE  OF  THE  SUN 172 

SOME  BRILLIANT  CONSTELLATIONS 192 

15 


LIST   OF   ILLUSTRATIONS 

PAGE 

THE  GREAT  NEBULA  IN  ORION 210 

THE  GREAT  SPIRAL  NEBULA         .         .  .        .216 

REGION  OF  THE  HEAVENS  IN  CANIS  MAJOR  .  .  .  220 
THE  GREAT  NEBULA.  IN  ANDROMEDA  ....  222 
AT  WORK  IN  GREENWICH  OBSERVATORY  264 


DIAGRAMS 

FIG.  1.  ORBIT  AND  PHASES  OF  THE  MOON  .  .  .41 
„  2.  COMPARATIVE  VELOCITIES  OF  THE  PLANETS  .  62 
„  3.  SURFACE- GRAVITY  ON  THE  VARIOUS  PLANETS  .  65 
„  4.  ORBIT  AND  PHASES  OF  AN  INFERIOR  PLANET  .  73 
„  5.  SHOWING  HOW  THE  TAIL  OF  A  COMET  is 

DIRECTED  AWAY  FROM  THE  SuN     ,         .          .156 

„     6.  PASSAGE    OF  THE  EARTH   THROUGH  A  METEOR 

SWARM          .        .     " 163 

,,     7.  TOTAL  AND  PARTIAL  ECLIPSES  OF  THE  MOON   .     174 
„     8.  TOTAL  ECLIPSE  OF  THE  SUN     .         .         .         .176 


16 


G*    THi 

UNIVSFT" 


THE  ROMANCE  OF  MODERN 
ASTRONOMY 

CHAPTER   I 
OUR   PLACE   IN   THE  UNIVERSE 

Q^CIENCE  is  the  study  of  Nature.  By  means  of 
v"^  science  we  are  enabled  to  understand  the  everyday 
things  of  life — the  flowers,  the  hills,  the  stars — and 
the  place  which  they  occupy  in  Nature.  Thus,  botany  is 
the  study  of  the  flowers  and  trees  ;  geology  is  the  study  of 
the  hills  and  rocks ;  while  astronomy  raises  our  thoughts 
to  the  star-spangled  heavens. 

Of  all  the  sciences — and  they  are  many  and  varied — 
astronomy  is  the  most  interesting  and  the  most  wonderful. 
Not  only  is  it  full  of  interest,  but  it  is  in  many  ways  the 
most  educative  study  which  the  human  mind  can  pursue ; 
for  it  enables  us  to  understand  the  position  which  our 
world  occupies  in  the  Universe.  By  astronomy  men 
were  enabled  to  answer  the  question,  "What  is  the 
Earth?1' 

In  childhood  we  learn  that  "  the  Earth  is  round  like  an 
orange  or  a  ball,1'  but  when  we  stand  out  in  the  open  and 
look  around  us,  the  Earth  seems  more  like  a  vast  illimit- 
able plain  than  a  round  globe.  Long  ago,  in  the  child- 
hood of  the  race,  men  believed  our  world  to  be  a  vast 

17  B 


OUR  PLACE   IN    THE  UNIVERSE 

illimitable  plain,  but  reflective  minds  were  not  satisfied 
with  this  theory.  They  soon  perceived  that  the  Earth 
was  not  a  plain.  The  Sun,  it  was  observed,  rose  in  the 
east  every  morning,  and  set  in  the  west  every  evening,  and 
it  was  obvious  that  it  could  not  rise  and  set  through  the 
solid  ground.  The  question  presented  itself  to  those 
early  Chaldean  and  Greek  students  of  Nature, — Where  did 
the  Sun  go  every  night  ?  Did  it  pass  under  the  Earth  ? 
Such  an  idea  was  unthinkable  to  those  early  scientists. 
Was  not  the  Earth  solid  and  immovable,  firmly  fixed  at 
the  bottom  of  Creation  ?  Accordingly  some  very  re- 
markable theories  were  devised  to  explain  how  the  Sun 
rose  in  the  east  in  the  morning,  after  having  disappeared 
in  the  west  the  previous  evening.  Some  of  the  ancients 
believed  that  the  Sun  fell  into  the  sea  at  night  and  was 
quenched,  and  that  the  gods  were  busy  all  night  making 
a  new  Sun  to  start  the  next  morning  in  the  east.  But, 
as  Sir  Robert  Ball  remarks,  "this  was  thought  to  be 
such  a  waste  of  good  Suns  that  a  more  economic  theory 
was  afterwards  proposed."  This  was  that,  as  the  Sun  was 
falling  into  the  ocean  in  the  west,  it  was  caught  by  the 
god  Vulcan,  who  was  waiting  in  his  boat  to  prevent  it 
falling  into  the  sea.  Having  placed  the  orb  of  day  in  his 
boat,  Vulcan  rowed  round  by  the  north,  where  a  great 
ocean  was  supposed  to  exist.  Arriving  in  the  east,  he 
pitched  the  Sun  into  the  sky  with  tremendous  force,  to 
commence  another  day's  journey. 

Theories  such  as  these  had  influence  for  many  years 
over  the  minds  of  men.  Gradually,  however,  it  became 
apparent  that  such  ideas  were  absurd,  and  that  the  Sun 
must  really  go  below  the  Earth.  And  here  students 
of  Nature  asked — What  is  the  Earth,  and  what  supports 
it  ?  Many  grotesque  theories  were  put  forward.  One 

18 


OUR  PLACE   IN   THE  UNIVERSE 

speculator  thought  that  the  Earth  was  held  up  by  great 
pillars,  which  allowed  the  Sun  to  pass  between  them ; 
another  believed  our  world  to  be  supported  by  enormous 
mythical  animals.  Some  support,  in  the  minds  of  the 
ancients,  was  absolutely  necessary.  The  author  of  the 
Book  of  Job,  however,  had  grasped  the  truth,  for, 
writing  of  the  power  of  the  Creator,  he  says,  "He 
hangeth  the  Earth  upon  nothing." 

This  is  literally  true  ;  the  Earth  hangs  upon  nothing. 
Gradually  the  truth  dawned  that  the  Earth  was  a  globe, 
not  a  vast  plain — a  view  which  was  held  by  the  great 
Greek  philosopher,  Aristotle,  and  became  generally  ac- 
cepted. Aristotle  thought  that  the  Earth,  a  globe  sus- 
pended in  space,  was  the  centre  of  the  universe,  round 
which  the  Sun,  Moon,  and  stars  revolved.  By  this  time 
considerable  progress  had  been,  made  in  the  study  of 
astronomy.  The  study  of  the  stars  had  become  a  science 
of  measurement,  and  it  was  soon  apparent  that  the  celestial 
bodies  had  not  one  motion  round  the  Earth  only,  but  a 
number  of  motions.  For  instance  it  was  known  that  the 
Sun,  Moon,  and  stars  revolved  round  the  Earth  every 
twenty-four  hours.  But  it  soon  became  apparent,  as 
observation  progressed,  that  the  Moon  had  another  motion 
round  the  Earth  once  in  a  month  ;  and  that  the  Sun  seemed 
to  have  also  another  motion,  revolving  round  the  Earth 
once  in  a  year.  Then  attentive  observation  of  the  heavens 
disclosed  the  existence  of  another  class  of  objects.  The 
ordinary  stars — "  fixed  stars  "  as  they  came  to  be  called — 
revolved  once  in  twenty-four  hours.  But  they  did  not 
change  their  positions  relative  to  each  other.  The  star- 
groups  or  constellations  remained  unchanged.  The  early 
astronomers  noted  that  there  were  five  bright  star-like 
objects,  which,  instead  of  remaining  fixed  in  the  sky, 

19 


OUR  PLACE   IN   THE   UNIVERSE 

moved  in  an  irregular  manner  round  the  heavens,  always 
keeping  close  to  the  path  traversed  by  the  Sun  on  its 
annual  journey.  These  the  early  observers  named 
"  planets,"  which  is  Greek  for  "  wanderers."  It  was  soon 
recognised  that  there  were  five  of  these  objects,  each 
different  from  the  other.  There  was  Venus,  the  brightest 
of  the  wanderers,  shining  with  a  soft,  gentle,  steady  light, 
named  by  the  ancient  Greeks  after  their  goddess  of 
love.  They  noticed  that  Venus  never  moved  far  from  the 
Sun — that  it  was  never  to  be  seen  shining  on  a  really  dark 
sky.  It  was  also  observed  that  Venus  was  sometimes 
visible  as  an  evening  star  after  sunset,  and  sometimes  as 
a  morning  star  before  sunrise.  Indeed  it  was  long  thought 
that  the  morning  star  and  the  evening  star  were  separate 
bodies ;  but  very  early  in  astronomical  history  it  was 
recognised  that  they  were  one  and  the  same.  The  ancients 
recognised  another  bright  object  also  visible  as  an  evening 
and  morning  star,  and  keeping  much  closer  to  the  Sun  than 
Venus.  They  called  the  planet  Mercury,  "  the  messenger 
of  the  gods."  But  they  also  called  it  "  the  sparkling 
one,"  from  its  rapidly  twinkling  light.  Another  bright 
object,  much  brighter  than  Mercury,  was  also  recognised 
— a  great  golden  star,  which,  instead  of  keeping  close  to 
the  Sun,  swept  majestically  round  the  entire  heavens.  This 
they  named  Jupiter  after  their  chief  deity.  Then  they 
recognised  a  planet  of  reddish  hue  which  at  times  waxed 
almost  as  bright  as  Jupiter,  then  rapidly  waned.  From 
its  fiery  colour  they  named  this  object  Mars,  after  the 
god  of  war.  Yet  another  planet,  fainter  than  the  rest — 
slow  moving — of  a  dull  yellowish  light,  creeping  round  the 
entire  heavens  once  in  about  thirty  years,  was  named 
Saturn,  after  the  god  of  time. 

Each   of  these   planets   had   its  own  peculiarities  of 

20 


OUR  PLACE   IN  THE  UNIVERSE 

motion,  and  partook  also  in  the  revolution  of  the  entire 
heavens  once  in  twenty-four  hours.  The  problem  before 
the  ancient  astronomers  then  was  how  to  account  for  the 
motions  of  Sun,  Moon,  planets,  and  stars.  Many  and  varied 
were  the  explanations  put  forward.  Eudoxus,  a  Greek 
thinker  who  died  about  355  B.C.,  was  the  author  of  an 
ingenious  attempt  to  explain  these  motions  by  an  elaborate 
theory  known  as  that  of  the  spheres.  The  Earth,  he 
believed,  was  a  globe  firmly  fixed  at  the  centre  of  the 
universe.  Each  planet  was  fixed  to  a  number  of  different 
spheres  by  the  manipulation  of  which  the  elaborate 
motions  resulted.  Then  at  the  extreme  limit  of  the 
universe  was  a  sphere  to  which  all  the  stars  proper  were 
fixed. 

Another  theory  was  that  of  the  astronomer  Hipparchus, 
which  was  developed  to  its  greatest  extent  by  his  successor, 
Ptolemy,  of  Alexandria,  in  Egypt.  Like  Eudoxus,  Ptolemy 
believed  that  the  Earth  was  firmly  fixed  as  the  centre  of 
creation.  But  he  did  not  accept  the  theory  of  spheres. 
He  believed  that  the  Sun,  Moon,  planets,  and  stars  revolved 
round  the  Earth  in  the  following  order — the  Moon, 
Mercury,  Venus,  the  Sun,  Mars,  Jupiter,  Saturn,  and  the 
stars  proper,  which,  as  in  the  theory  of  Eudoxus,  were  sup- 
posed to  be  attached  to  the  inside  of  a  large  sphere.  But 
Ptolemy  was  not  ignorant  of  the  irregularities  in  the 
motions  of  the  planets,  of  the  fact  that  the  planets  did 
not  move  with  uniform  velocities.  He  was  one  of  the  most 
thoughtful  of  the  ancient  astronomers,  and  he  knew  that 
if  a  planet  moved  round  the  Earth  in  a  uniform  circular 
orbit,  its  velocity  and  direction  would  not  change.  Accord- 
ingly he  devised  a  most  complicated  and  ingenious  theory 
— that  the  planets  moved  in  circles,  and  that  the  centres 
of  these  circles  revolved  round  the  Earth  in  larger  circles. 

21 


OUR   PLACE   IN  THE  UNIVERSE 

The  smaller  circles  were  called  epicycles.  As  new  irregu- 
larities came  to  be  discovered,  new  epicycles  had  to  be 
invented,  until  at  last  the  theory  became  so  difficult  and 
cumbersome  that  few  could  understand  it.  Indeed  it  is 
recorded  of  a  certain  King  of  Spain  that  when  his  tutor 
was  explaining  to  him  the  theory  then  generally  accepted, 
he  exclaimed  in  disgust  that  if  he  had  been  consulted  at 
the  Creation,  he  could  have  given  some  useful  hints  for 
simplifying  the  system  of  the  Universe. 

In  spite  of  the  intricacies  and  improbabilities  of 
Ptolemy's  theory,  it  was  accepted  for  fourteen  hundred 
years.  It  is  true  that  some  keen  minds  among  the 
Greeks  had  come  to  the  conclusion  that  there  was  a 
much  simpler  conception  of  the  Universe ;  but  they 
had  not  the  courage  to  declare  for  a  new  theory,  and 
it  was  left  for  Nicolaus  Copernicus,  a  Polish  clergyman, 
to  propound  the  system  which  bears  his  name.  Coper- 
nicus, after  giving  deep  attention  to  the  subject,  came 
to  the  conclusion  that  it  was  much  easier  to  believe 
that  the  Earth  turned  on  its  own  axis,  and  so  caused 
an  apparent  motion  of  Sun,  Moon,  planets,  and  stars, 
than  to  think  that  these  objects  all  happened  by  some 
coincidence  to  go  round  our  planet  in  exactly  the  same 
time.  Copernicus  also  came  to  the  conclusion  that, 
instead  of  the  Sun  moving  round  the  Earth  once  a  year, 
and  the  planets  also  revolving  round  our  world  in 
complicated  orbits,  it  was  more  reasonable  to  believe 
that  the  Earth  and  the  other  planets  revolved  round 
the  Sun.  This  was  the  theory,  which  Copernicus  put 
forward.  It  had  the  merit  of  simplicity,  but  notwith- 
standing this  fact,  it  was  disbelieved,  and  its  supporters 
were  threatened  with  persecution.  Nevertheless,  men  of 
science  were  driven  to  accept  it,  because  they  saw  how 


OUR  PLACE  IN  THE   UNIVERSE 

greatly  its  acceptance  simplified  the  complicated  motions 
of  the  planets.  Tycho  Brahe,  the  famous  Danish  astro- 
nomer, abandoned  the  idea  that  the  planets  revolved 
round  our  Earth,  choosing  to  believe  that  they  revolved 
round  the  Sun,  which  moved  round  our  planet.  The 
next  step  was  to  declare  boldly  that  the  theory  of 
the  Earth's  motion  explained  more  satisfactorily  the 
motions  of  the  celestial  bodies.  This  step  was  taken 
by  Bruno,  Galileo,  and  Kepler.  But  it  was  taken  at 
a  great  risk,  and  at  a  great  sacrifice.  Bruno  was  burned 
alive  for  holding  this  theory  among  others  which  the 
Roman  Catholic  Church  had  pronounced  to  be  impious. 
Galileo  had  to  suffer  much  persecution  for  his  champion- 
ship of  the  Copernican  theory.  Its  opponents  disliked 
Galileo  most  of  all,  because  he  brought  forward  un- 
answerable arguments  in  favour  of  the  new  system. 
Kepler,  the  least  persecuted  of  the  three,  was  destined 
still  further  to  improve  the  theory  by  his  famous  "  three 
laws."  He  showed  that  the  Earth  and  the  other  planets, 
instead  of  revolving  round  the  Sun  in  circular  paths, 
moved  in  ellipses.  He  was  enabled  to  explain  many 
of  the  irregularities  which  Copernicus  had  to  leave  un- 
solved. Thus  the  labours  of  Copernicus,  Galileo,  and 
Kepler  showed  us  beyond  a  doubt  our  true  position  in 
the  universe — that  the  Earth  is  merely  a  planet  in  con- 
stant revolution  round  the  Sun,  a  member  of  the  Sun's 
system,  and  a  companion  planet  of  Mercury  and  Venus, 
Mars,  Jupiter,  and  Saturn. 

It  was  Sir  Isaac  Newton  who  demonstrated  beyond 
doubt  the  truth  of  the  system  of  Copernicus.  Newton 
furnished  mankind  with  a  key  to  unlock  the  mysteries 
of  the  Solar  System  ;  he  explained  why  the  Earth  and 
the  other  planets  were  constantly  moving  round  the  Sun, 

23 


OUR  PLACE   IN   THE   UNIVERSE 

and  why  they  moved  in  elliptical  orbits.  It  was  in  the 
year  1666,  when  Newton  was  a  young  man  in  his  an- 
cestral home  near  Grantham,  in  England,  that  his  mind 
first  lit  on  the  grand  idea  of  the  law  of  gravitation— 
that  every  particle  of  matter  in  the  universe  attracts 
every  other  particle.  The  story  goes  that  one  day 
when  Newton  was  sitting  in  his  garden  he  saw  an  apple 
fall  to  the  ground.  Now,  he  knew  why  the  apple  fell — 
because  it  was  heavy  ;  in  other  words,  because  it  was 
drawn  to  the  Earth  by  the  power  of  gravitation.  And 
he  was  led  to  ask  if  the  same  force  did  not  keep 
the  Moon  in  its  monthly  orbit  round  the  Earth,  and 
prevent  it  flying  off  into  space,  and  also  keep  the 
Earth  and  the  other  planets  in  their  paths  round  the 
Sun.  After  twenty  years1  hard  mathematical  work,  he 
was  able  to  prove  that  the  force  which  drew  the  apple 
to  the  ground  held  the  Moon  in  its  orbit ;  and  that 
the  Moon  moved  round  the  Earth,  and  the  Earth  and 
the  other  planets  round  the  Sun,  simply  by  virtue  of 
the  inherent  power  of  gravity  in  these  various  bodies. 
For  instance,  the  Earth  attracts  the  Moon,  and  the 
Moon  attracts  the  Earth ;  but  the  Earth  is  so  much 
larger  than  the  Moon  that  our  satellite  is  compelled 
to  revolve  round  our  world.  Similarly  the  Sun  attracts 
the  Earth,  and  the  Earth  attracts  the  Sun,  but  owing 
to  the  immense  superiority  of  the  Sun  in  size,  the 
Earth,  though  having  a  natural  tendency  to  move  in 
a  straight  line,  is  compelled  to  move  round  the  larger 
body. 

Thus  Copernicus  showed  us  our  Earth's  position  in 
the  Solar  System,  and  Newton  showed  us  why  we  occupy 
that  position.  The  result  of  the  change  in  astronomical 
thought  was  that  the  Earth's  inhabitants  could  no  longer 


OUR  PLACE   IN  THE  UNIVERSE 

consider  themselves  the  chief  objects  of  creation.  Our 
world  was  brought  down  from  the  position  of  ruler 
and  centre  of  the  universe  to  the  humble  place  of  a 
small  planet  revolving  round  the  Sun.  As  we  shall 
find  in  the  following  chapters,  this  was  but  the  first 
step  in  the  change  of  opinion,  for  the  researches  of 
Sir  William  Herschel  and  later  astronomers  have 
proved  that  our  planet  is  a  mere  grain  of  sand  in 
the  ocean  of  infinity.  Astronomy  enables  us  to  under- 
stand the  fact — though  we  but  imperfectly  realise  it 
— that  our  Earth,  which  seems  to  us  a  great  flat  im- 
movable plain,  is  in  reality  a  globe  about  8000  miles 
in  diameter,  turning  on  its  own  axis  in  twenty-four 
hours,  and  dashing  onward  in  its  orbit  round  the  Sun 
at  the  rate  of  eighteen  miles  a  second.  We  do  not 
feel  the  motion  of  our  planet,  because  we  are  carried 
along  with  it,  and  the  atmosphere  is  also  a  component 
part  of  our  globe.  It  is  difficult  to  grasp  the  fact 
that  our  planet  is  moving  onwards  with  so  great  a 
velocity,  that  each  second  of  time  finds  us  eighteen 
miles  onward  on  our  journey.  Thus  we  see  that 
astronomy,  alone  of  the  sciences,  answers  the  question 
— What  is  our  Earth,  and  what  is  its  position  in 
Nature  ? 


CHAPTER   II 
EFFECTS    OF   THE   EARTH'S    MOTIONS 

THE  motion  of  the  Earth  is  the  magic  key  which  un- 
locks the  door  of  the  mysteries  of  the  everyday 
phenomena  of  Nature.  Day  and  night,  the  seasons, 
twilight,  "the  midnight  Sun,"  the  long  polar  night,  all 
these  phenomena  are  easily  understood  when  we  regard 
them  in  the  light  of  the  rotation  of  the  Earth  on  its  axis, 
the  inclination  of  this  axis,  and  the  revolution  of  the 
Earth  round  the  Sun. 

To  the  first  of  these  facts,  the  rotation  of  the  Earth,  we 
are  indebted  for  the  phenomenon  of  day  and  night.  The 
Earth  is  constantly  whirling  round  on  its  axis  from  west 
to  east,  and  the  result  is  the  apparent  motion  of  the 
heavenly  bodies  from  east  to  west.  By  this  motion  of 
rotation  we  get  the  first  and  most  obvious  measure  of 
time — the  day  which  measures  in  length  only  a  few 
minutes  under  twenty-four  hours. 

A  good  idea  of  the  rapid  rate  at  which  the  Earth  is 
turning  on  its  axis  may  be  had  by  pointing  a  telescope 
to  a  star,  and  by  noticing  how  swiftly  the  star  passes  out 
of  the  field  of  view.  At  sunrise  and  sunset,  too,  we 
notice  plainly  the  difference  made  by  a  few  minutes. 
Owing  to  the  fact  that  the  Earth  has  an  atmosphere,  day- 
light does  not  disappear  whenever  the  Sun  sinks  below 
the  horizon.  The  rays  of  the  Sun  still  strike  the  upper 
regions  of  our  atmosphere,  and  thus  we  have  twilight  and 

26 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

the  gradual  darkening  of  the  sky  and  disappearance  of 
daylight. 

The  chief  effect  of  the  Earth's  revolution  round  the  Sun 
— an  effect  which  affects  the  periods  of  light  and  darkness 
— is  the  change  of  the  seasons,  spring,  summer,  autumn, 
and  winter.  This  ceaseless  cycle,  to  which  the  Earth's 
inhabitants  are  so  accustomed  that  they  scarcely  stop 
to  ask  themselves  the  why  and  wherefore,  is  due  chiefly 
to  one  astronomical  fact.  The  axis  of  the  Earth — 
the  imaginary  line  joining  the  north  and  south  poles — 
is  inclined  to  the  orbit  of  our  planet  by  about  sixty- 
seven  degrees.  This  explains  the  seasons  and  the 
differing  lengths  of  day  and  night  on  the  various  parts 
of  the  Earth.  Most  of  us  have  heard  of  such  phenomena 
as  the  long  polar  night,  the  midnight  Sun,  &c.,  but  few 
really  understand  that  these  phenomena  are  due  to  the 
same  causes  which  give  us  our  long  periods  of  daylight 
in  summer  and  of  darkness  in  winter. 

At  the  spring  equinox,  day  and  night  are  equal  all 
over  the  world — at  the  poles  and  the  equator.  At  this 
period  both  poles  of  the  Earth  are  equally  exposed  to  the 
solar  rays.  Neither  is  tilted  towards  the  Sun  more  nor 
less  than  the  other.  But  as  the  Earth  moves  gradually 
round,  the  northern  hemisphere  becomes  more  and  more 
inclined  towards  the  solar  beams,  while  the  southern 
hemisphere  is  more  and  more  inclined  away  from  the  orb 
of  day.  Spring  is  giving  place  to  summer.  At  the  summer 
solstice  the  northern  hemisphere  is  tilted  towards  the  Sun 
at  its  greatest  inclination  while  it  is  midwinter  in  the  south. 
The  days  and  nights  were  equal  at  the  spring  equinox  ;  at 
the  summer  solstice  the  days  are  much  longer  than  the 
nights  in  the  northern  hemisphere,  the  opposite  being 
the  case  in  the  south.  After  the  21st  of  June  the  period 

27 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

of  darkness  increases  in  the  northern  hemisphere  and 
decreases  in  the  southern,  until  on  the  21st  of  September 
daylight  and  darkness  are  equal  all  over  the  globe.  In 
its  cycle  of  change  the  axis  of  the  earth  is  again  upright 
relative  to  the  Sun.  After  the  autumn  equinox  is  past, 
the  northern  hemisphere  tilts  more  and  more  away  from 
the  Sun,  while  the  southern  comes  more  and  more  into 
sunlight.  The  result  is  that  by  the  21st  of  December, 
when  the  winter  solstice  is  reached,  the  northern  hemi- 
sphere has  a  short  period  of  daylight  and  a  long  period 
of  darkness,  while  the  reverse  state  of  affairs  takes  place 
in  the  south.  The  northern  hemisphere  is  tilted  from 
the  Sun  at  its  greatest  tilt.  After  the  winter  solstice  the 
period  of  daylight  increases  in  the  northern  hemisphere 
and  decreases  in  the  southern,  until  we  come  again 
to  the  21st  of  March,  when  at  the  spring  equinox  day 
arid  night  are  equal  all  over  the  world. 

In  the  early  ages  of  the  world,  before  astronomy  had 
been  developed,  men  did  not  understand  this  revolution  of 
our  dwelling-place  round  the  Sun.  They  only  knew,  just 
as  the  unlearned  know  to-day,  that  at  the  winter  solstice, 
in  the  middle  of  December,  the  Sun  rose  in  the  south-east, 
moved  across  the  southern  sky,  rising  to  a  low  altitude 
above  the  horizon,  and  set  in  the  south-west  in  the  after- 
noon. We  notice  that  after  the  solstice  is  past,  the  Sun 
rises  a  little  earlier  each  morning  and  sets  a  little  later 
each  evening,  that  it  rises  farther  east  each  morning, 
and  sets  farther  west  each  evening,  until  on  the  21st  of 
March  the  orb  of  day  rises  exactly  in  the  east  and  sets 
exactly  in  the  west.  Likewise  we  notice  that  as  more  and 
more  is  seen  of  the  Sun,  the  Earth  wakens  out  of  its 
winter  sleep.  Trees  begin  to  bud,  grass  to  grow — in 
short,  Nature  revives.  As  one  writer  puts  it :  "  The 

28 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

melting  of  'the  ice  and  snow,  the  gradual  reviving  of 
brown  soils,  the  flowing  of  sap  through  branches  apparently 
lifeless,  the  mist  of  foliage  beginning  to  enshroud  every 
twig  until  the  whole  country  is  enveloped  in  a  soft  haze 
of  palest  green  and  red — all  these  are  Nature's  signs  of 
spring." 

Then  as  spring  gradually  passes  into  summer,  the  Sun 
rises  every  morning  a  little  farther  north,  and  sets  every 
evening  a  little  farther  north,  while  every  day  it  rises 
higher  and  higher  in  the  sky.  Then  on  the  21st  of  June, 
the  "  longest  day,1'  it  rises  north-east  and  sets  north-west, 
and  is  about  eighteen  hours  above  the  horizon.  This  is 
the  period  of  longest  daylight,  because,  as  explained,  the 
northern  hemisphere  is  turned  directly  towards  the  Sun, 
but  the  period  of  greatest  heat  is  about  a  month  later 
in  coming.  If  the  Earth  and  the  atmosphere  could  retain 
none  of  the  heat  which  is  showered  down  from  the  Sun, 
the  period  of  greatest  heat  would  exactly  coincide  with 
the  summer  solstice.  However,  the  accumulation  of 
heat  retards  the  time  of  the  greatest  heat  until  about 
a  month  after  the  solstice — the  end  of  July  and  beginning 
of  August.-  Similarly  the  period  of  greatest  cold  is  a 
month  later  than  that  of  least  sunlight — the  end  of 
January  and  the  beginning  of  February. 

Gradually  summer  passes  into  autumn.  After  the 
summer  solstice  is  past,  the  Sun  begins  to  rise  later  and 
later  every  morning  and  sets  a  little  earlier  every  evening  ; 
and  in  addition,  the  orb  of  day  does  not  rise  so  high 
in  the  heavens.  This  continues  until  the  autumn 
equinox,  when  the  sun  rises  due  east  and  sets  due  west. 
In  fact,  day  and  night  are  equal  all  over  the  world,  and 
the  conditions  are  the  same  as  those  at  the  spring 
equinox.  But  there  is  one  difference.  The  weather  at 

29 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

the  spring  equinox  is  generally  cold  and  uncertain,  while 
at  the  corresponding  jxiriod  in  autumn  it  is  summer-like 
and  pleasant.  This  is  due  to  the  same  cause  which  was 
previously  mentioned,  that  after  summer  solstice  the  Earth 
continues  to  store  up  heat,  while  after  winter  the  Earth 
is  slow  to  absorb  heat.  In  short,  the  autumn  equinox 
generally  takes  place  in  summer-like  weather.  As  an 
American  astronomer  expresses  it :  "  Not  until  falling 
leaves  begin  to  flutter  about  our  feet,  and  grapes  and 
apples  ripen  in  orchard  and  vineyard,  do  we  realise  that 
autumn  is  really  here — that  everything  is  mellow  and 
finished.  Our  hemisphere  is  turning  yet  farther  away 
from  that  Sun  on  which  all  growth  and  development 
depend.  When  trees  are  a  glory  of  red  and  yellow  and 
russet  brown,  when  corn  stands  in  full  shocks  in  fields, 
and  day  after  day  of  warmth  and  sunshine  follow  through 
royal  October — it  seems  impossible  to  believe  that  slowly 
and  surely  winter  can  be  approaching.  But  soon  chilly 
winds  whistle  through  trees  from  which  the  bright  leaves 
are  almost  gone ;  a  thin  skin  of  ice  crystals  shoots  across 
wayside  pools  at  evening,  and  speedily  shivering  winter  is 
upon  us.  Just  before  Christmas  this  part  of  our  Earth 
is  tipped  its  farthest  away  from  the  Sun.  Then  for  a 
few  days  the  hours  of  darkness  are  at  their  longest.  The 
sap  has  withdrawn  far  into  the  roots  of  the  trees  until 
the  cold  shall  abate  ;  leaden  skies  drop  snowflakes,  and 
earth  sleeps  under  a  mantle  of  white." 

This  description  applies  only  to  the  temperate  zones 
of  the  Earth.  As  we  go  northwards  we  approach  the 
exaggerated  aspects  of  the  same  phenomena — the  mid- 
night Sun  and  the  long  polar  night.  The  cause  of  these 
phenomena  is  a  source  of  difficulty  to  many,  but  it  is 
quite  easily  understood  with  a  little  thought. 

30 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

At  midnight  in  the  end  of  June,  in  Scotland  there  is 
very  little  darkness.  The  sky  never  grows  actually  dark. 
We  seem  to  see  the  glow  of  the  Sun  almost  up  to 
midnight  after  it  sinks  in  the  north-west.  As  we  go 
farther  north  we  see  more  and  more  of  the  Sun.  We 
follow  it  farther  and  farther  until  it  just  goes  below 
the  horizon,  and  no  more.  Still  farther  north  it  skirts 
the  horizon,  and  is  visible  all  night  at  the  sixty-sixth 
parallel  of  latitude.  Beyond  this  the  Sun  does  not  dis- 
appear at  all  in  summer,  and  there  are  six  months  of 
daylight. 

The  phenomenon  of  the  midnight  Sun  draws  many  to 
the  northern  parts  of  Sweden,  Norway,  and  Russia,  where 
for  a  few  days  at  the  summer  solstice  the  sun  merely 
skirts  the  northern  horizon.  A  good  description  of  the 
midnight  Sun  is  given  by  Paul  du  Chaillu  in  his  account 
of  his  travels  in  Scandinavia :  "  The  brilliancy  of  the 
splendid  orb  varies  in  intensity,  like  that  of  sunset  and 
sunrise,  according  to  the  state  of  moisture  of  the  atmos- 
phere. One  day  it  will  be  of  a  deep-red  colour,  tingeing 
everything  with  a  roseate  hue  and  producing  a  drowsy 
effect.  There  are  times  when  the  changes  in  the  colour 
between  the  sunset  and  the  sunrise  might  be  compared  to 
the  variations  of  a  charcoal  fire,  now  burning  with  a  fierce 
red  glow,  then  fading  away  and  rekindling  with  greater 
brightness. 

"There  are  days  when  the  Sun  has  a  pale,  whitish 
appearance,  and  when  even  it  can  be  looked  at  for  six  or 
seven  hours  before  midnight.  As  this  hour  approaches, 
the  Sun  becomes  less  glowing,  gradually  changing  into 
more  brilliant  shades  as  it  dips  towards  the  lowest  point 
of  its  course.  Its  motion  is  very  slow,  and  for  quite  a 
while  it  apparently  follows  the  line  of  the  horizon,  during 

31 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

which  there  seems  to  be  a  pause,  as  when  the  Sun  reaches 
noon.  This  is  midnight.  For  a  few  minutes  the  glow  of 
sunset  mingles  with  that  of  sunrise,  and  one  cannot  tell 
which  prevails ;  but  soon  the  light  becomes  slowly  and 
gradually  more  brilliant,  announcing  the  birth  of  another 
day.  .  .  .  How  beautiful  was  the  midnight.  How  red 
and  gorgeous  was  the  Sun !  How  drowsy  was  the  land- 
scape ;  Nature  seemed  asleep  in  the  midst  of  sunshine ; 
crystal  dewdrops  glittered  like  precious  stones  as  they 
hung  from  the  blades  of  grass,  the  petals  of  wild  flowers, 
and  the  leaves  of  the  birch  trees." 

Farther  north  the  Sun  is  constantly  visible  and  the 
north  pole  has  six  months1  continuous  light.  But  there 
is  another  side  to  the  picture.  For  six  months  there  is 
continuous  night,  and  even  in  the  north  of  Sweden, 
Norway,  and  Russia  there  are  days  in  midwinter  when 
the  Sun  does  not  rise,  just  as  in  summer  there  are  days 
when  it  does  not  set.  Du  Chaillu,  after  describing  the 
midnight  sun,  has  the  following  remarks  on  the  winter  in 
the  same  region,  which  is  worth  quoting  :  "  The  grass  turns 
yellow ;  the  leaves  change  their  colour  and  wither  and 
fall ;  the  swallows  and  other  migrating  birds  fly  towards 
the  south ;  twilight  comes  once  more ;  the  stars,  one  by 
one,  make  their  appearance,  shining  brightly  in  the  pale- 
blue  sky ;  the  Moon  shows  itself  again  as  the  queen  of 
night,  and  lights  and  cheers  the  long  and  dark  days  of 
the  Scandinavian  winter.  The  time  comes  at  last  when 
the  Sun  disappears  entirely  from  sight ;  the  heavens 
appear  in  a  blaze  of  light  and  glory,  and  the  stars  and  the 
Moon  pale  before  the  Aurora  Borealis." 

Such  are  the  various  phenomena  resulting  from  the 
fact  that  the  axis  of  the  Earth  is  inclined  to  the  plane, 
or  level,  of  its  orbit.  Were  the  axis  upright,  there 


THE  AURORA  BOREALIS 

The  aurora,  which  illuminates  the  long  winter  nights  of  the  far  North,  is  one  of 
the  most  wonderful  sights  in  the  skies.  Sometirres  seen  in  our  latitudes,  it  is  seen 
to  most  advantage  in  the  far  North.  Of  an  undoubted  electrical  origin,  it  varies  in 
harmony  with  the  sun-spot  period  about  every  eleven  years.  Hbr 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

would  be  no  seasons,  no  spring-time,  no  summer,  no 
autumn,  no  winter  season ;  there  would  be  no  midnight 
Sun  and  no  long  polar  night.  In  fact  the  continuous 
state  of  affairs  would  be  an  everlasting  springtime  without 
the  charm  of  our  earthly  spring.  This  seems  to  be  the 
state  of  affairs  on  Jupiter,  where  the  axis  is  nearly  per- 
pendicular to  the  planet's  orbit. 

Another  fact  has  also  something  to  do  with  the  seasons, 
though  only  in  a  modified  degree.  As  the  orbit  of  the 
Earth  is  not  a  perfect  circle,  but  an  ellipse,  the  Earth  is 
at  one  point  of  its  orbit  nearer  to  the  Sun  than  at  the 
other.  The  Earth  is  nearer  to  the  Sun  by  three  million 
miles  in  our  winter  than  in  our  summer.  At  first  this 
seems  a  paradox,  that  the  time  of  closest  approach  to 
the  orb  of  day  is  the  time  of  greatest  cold.  A  little 
consideration,  however,  soon  disposes  of  the  difficulty. 
In  the  northern  hemisphere  the  decreased  distance  of 
the  Sun  modifies  the  severities  of  winter,  while  its 
increased  distance  mitigates  the  heat  of  summer. 

In  the  southern  hemisphere,  on  the  other  hand,  the 
time  of  greatest  heat  takes  place  when  the  Sun  is  nearest, 
and  the  time  of  greatest  cold  when  the  Sun  is  at  its 
greatest  distance.  Thus  the  climate  in  the  northern 
hemisphere  is  rendered  more  equable  than  that  in  the 
south. 

Thus  we  understand  that  it  is  owing  to  the  inclination 
of  the  axis  of  the  Earth  that  the  Sun's  apparent  path 
in  the  heavens,  the  ecliptic,  is  tilted,  and  that  the 
Sun  rises  so  much  higher  in  the  sky  in  summer  than 
in  winter.  A  similar  line  of  reasoning  applies  to  our 
satellite  the  Moon.  There  is  much  less  moonlight  in 
summer  than  in  winter.  At  a  first  consideration  it 
seems  as  if  this  was  owing  to  increased  daylight,  the 

33  c 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

moonlight  not  being  required,  and  consequently  not 
noticed ;  but  such  is  not  the  case.  There  is  really 
less  moonlight  in  summer  than  in  winter.  This  arises 
from  the  fact  that  before  the  Moon  can  be  "  full " 
and  shining  with  complete  radiance,  it  must  be  "  in 
opposition"  to  the  Sun,  that  is,  situated  in  the  dia- 
metrically opposite  portion  of  the  sky.  In  winter  the 
Sun  is  traversing  the  lower  zodiacal  constellations,  and 
as  a  result  the  Moon  at  the  full  phase  passes  through 
the  higher.  The  full  Moon  at  midwinter  has  the  same 
situation  as  the  Sun  at  midsummer.  Thus  in  winter 
we  get  more  moonlight  than  sunlight.  In  summer  the 
conditions  are  reversed.  The  Sun  is  in  the  higher  con- 
stellations ;  consequently  the  full  Moon  at  midsummer 
occupies  the  place  of  the  Sun  at  midwinter,  and  thus 
there  is  more  sunlight  than  moonlight.  Instead  of 
shining  from  on  high  with  silvery  radiance,  the  Moon, 
in  summer,  creeps  through  the  lower  constellations, 
gleaming  with  a  golden  hue,  which  harmonises  with 
the  period  of  summer-time.  As  Mr.  Maunder  puts  it : 
"The  evasive  Moon  recognises  that  the  season  belongs 
by  right  to  her  more  powerful  brother,  and  timidly  skirts 
the  south  as  if  anxious  to  escape  notice."" 

The  apparent  yearly  motion  of  the  Sun  is  due  to 
two  causes — the  motion  of  the  Earth  and  the  inclination 
of  the  Earth's  axis.  The  apparent  motion  of  the  Sun 
is  not  itself  visible,  but  we  can  trace  it  in  an  apparent 
drift  of  the  stars  into  the  sunlight.  The  stars,  as  a 
result  of  the  Sun's  apparent  motion  amongst  them,  set 
four  minutes  earlier  each  night.  In  a  fortnight  or  a 
month  this  makes  an  appreciable  difference  in  the  aspect 
of  the  sky.  For  instance,  at  10  P.M.  in  the  beginning 
of  January,  Orion  and  the  winter  constellations  occupy 

34 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

prominent  positions  in  the  southern  heavens.  At  the 
same  hour  a  month  later  they  have  moved  considerably 
to  the  west,  while  in  March  they  are  beginning  to 
pass  over  towards  the  western  horizon.  By  watching 
these  changes  with  care  and  attention,  the  ancient  astro- 
nomers were  enabled  with  tolerable  accuracy  to  trace  the 
apparent  pathway  of  the  Sun  among  the  stars. 

A  word  may  be  said  here  as  to  the  difference  of 
the  day  measured  by  the  Sun — "the  solar  day" — and 
that  measured  by  the  stars — "  the  sidereal  day."  Sidereal 
time  is  the  exact  time  required  for  one  star  to  move 
from  the  meridian  round  to  the  meridian  again,  in  fact 
it  is  the  exact  time  required  by  the  Earth  to  rotate 
on  its  axis.  But  the  sidereal  day  is  not  the  ordinary 
day.  Were  the  Earth  standing  still  it  would  be  so. 
But  our  planet  not  only  whirls  round  on  its  axis ;  it 
is  also  moving  round  the  Sun.  As  a  consequence  of 
the  motion  of  the  Earth,  which  gives  rise  to  an  apparent 
motion  of  the  Sun,  the  Sun  appears  to  come  to  the 
meridian  four  minutes  later  each  day  if  we  reckon  time 
by  the  sidereal  clock.  In  other  words,  the  day  measured 
by  the  Sun  is  four  minutes  longer  than  the  day  measured 
by  the  stars,  and  the  difference  amounts  to  exactly  one 
day  in  each  year.  Now  sidereal  time  is  in  reality  the 
only  true  measurement  of  the  day,  because  it  is  the 
exact  time  of  the  rotation  of  the  Earth's  axis.  But 
it  is  impossible  to  measure  our  ordinary  time  by  this 
method.  Professor  Todd  puts  it  very  clearly  in  the 
following  words  :  "  Sidereal  noon  comes  at  all  hours  of 
the  day  and  night  during  the  progress  of  the  year. 
Plainly,  then,  sidereal  time  is  not  a  fit  standard  for 
regulating  the  affairs  of  ordinary  life,  for  while  it  would 
answer  for  a  fortnight  or  so,  the  displacement  of  four 

35 


EFFECTS  OF  THE  EARTH'S  MOTIONS 

minutes  daily  would  in  six  months  have  all  the  world 
breakfasting  after  sunset,  staying  awake  all  through 
the  night,  and  going  to  bed  in  the  middle  of  the 
forenoon.1"  The  difficulty  cannot  be  exactly  solved  by 
taking  the  solar  day  instead  of  the  sidereal,  for,  as 
Professor  Todd  says,  "  Begin  on  any  day  of  the  year 
and  observe  the  Sun's  transit  of  the  meridian  as  you 
did  that  of  a  star.  The  instant  when  the  sun's  centre 
is  on  the  meridian  is  known  as  apparent  noon.  If  you 
repeat  the  observation  every  day  for  a  year  and  com- 
pare the  intervals  between  successive  transits,  you  will 
find  them  varying  in  length  by  many  seconds,  because 
they  are  all  apparent  solar  days ;  they  will  not  all  be 
equal  as  in  the  case  of  the  star.  By  taking  the  average 
of  all  the  intervals  between  the  Sun's  transit — that  is, 
the  mean  of  all  the  apparent  solar  days  in  the  course 
of  the  year — an  invariable  standard  is  obtained  like 
that  from  the  stars  themselves."  Thus  we  have  the 
mean  solar  day  by  which  all  the  clocks  and  watches 
in  everyday  life  are  regulated. 


36 


CHAPTER  III 
THE   ORB   OF   NIGHT 

IN  early  times,  as  was  seen  in  the  previous  chapter, 
men  believed  that  the  Earth  was  the  centre  of  the 
Universe,  and  round  it  all  the  orbs  of  heaven  re- 
volved. To-day  we  know  that  only  one  celestial  body  owns 
allegiance  to  the  Earth.  That  orb  is  our  satellite,  the 
Moon,  which  goes  round  our  world  once  in  about  twenty- 
seven  days.  The  Moon's  revolution  round  the  Earth 
from  east  to  west  in  a  little  over  a  day  is  only  apparent, 
the  result  of  our  planet's  rotation  on  its  axis,  but  its 
motion  from  west  to  east  is  real. 

We  owe  much  to  the  Moon.  To  it  we  owe  the 
glorious  silvery  light  which  our  satellite  sheds  on  us.  As 
Flammarion  has  said  :  "  It  is  the  delightful  hour  when  all 
Nature  pauses  in  the  tranquil  calm  of  the  silent  night. 
The  Sun  has  cast  his  farewell  beams  upon  the  weary 
Earth.  All  sound  is  hushed.  And  soon  the  stars  will  shine 
out  one  by  one  on  the  bosom  of  the  sombre  firmament. 
Opposite  to  the  sunset  in  the  east  the  full  Moon  rises 
slowly,  as  it  were,  calling  our  thoughts  towards  the 
mysteries  of  Eternity,  while  her  lamp  light  spreads  over 
space  like  a  dew  from  heaven."  Not  only  is  the  moonlight 
useful,  it  is  exquisitely  beautiful. 

The  most  casual  observer  of  the  heavens  cannot  fail  to 
notice  that  as  the  Moon  moves  eastwards  in  the  heavens 
its  form  changes.  When  we  first  see  the  new  Moon  in 
the  western  sky  above  the  sunset,  it  is  a  slender  crescent 

37 


THE   ORB   OF   NIGHT 

of  silvery  light.  Night  after  night  it  grows  in  size  until 
about  five  days  after  we  first  see  it  it  is  half  full.  It  has 
reached  its  "First  Quarter.""  It  continues  to  grow  for 
about  another  week,  until  one  evening  it  rises  just  as  the 
Sun  sets,  and  reaches  the  meridian,  the  point  due  south, 
about  midnight ;  while  it  is  fully  illuminated  and  its 
round  disc  sheds  over  our  world  that  inimitable  light 
known  as  moonlight.  Then  slowly  its  size  decreases. 
It  rises  later  and  later,  and  grows  smaller  and  smaller, 
until  when  it  reaches  its  "  Last  Quarter  "  it  is  only  to  be 
seen  in  the  morning  hours.  And  then  it  draws  closer  to 
the  Sun  until  its  thin  little  crescent  is  lost  in  the  sunrise, 
to  emerge  some  days  from  the  sunset  as  "New  Moon." 

Those  who  do  not  give  the  matter  sufficient  considera- 
tion believe  that  the  Moon  actually  changes  its  shape  as 
it  moves  round  the  Earth.  Indeed  it  is  recorded  of  a 
novelist  that  he  wrote  of  a  star  shining  between  the  horns 
of  the  crescent  Moon ;  the  poet  Coleridge  makes  the 
same  mistake  in  the  "  Ancient  Mariner."  A  little  con- 
sideration, however,  will  show  that  there  is  no  real  change 
of  shape.  Like  our  own  world,  the  Moon  is  a  dark 
globe,  and  it  only  shines  by  the  reflected  light  of  the 
Sun.  Therefore,  only  one  half  of  the  globe  is  illumi- 
nated at  once.  Just  before  the  crescent  of  the  new  Moon 
appears,  when  the  Moon  is  between  the  Earth  and  the 
Sun,  the  dark  side  of  the  Moon  is  turned  to  the  Earth 
and  we  do  not  see  it.  At  First  Quarter  we  only  see  one 
half  of  our  satellite  illuminated.  As  the  Moon  moves 
eastward  we  see  more  and  more  of  the  illuminated  surface, 
until  at  full  Moon  the  orb  is  at  the  other  side  of  the  Earth 
from  the  Sun,  and  we  see  it  fully  illuminated.  Then 
as  it  draws  closer  to  the  Sun  we  see  less  and  less  of  the 
illuminated  surface,  until  it  becomes  once  again  invisible. 


THE  NEW  MOON  AND  THE  SETTING  SUN 


^P^R^^S 

Of   THF 
UNIVERSITY 

\  Of 


THE   ORB   OF   NIGHT 

What  is  the  distance  of  the  Moon  ?  That  is  the  first 
question  which  presents  itself  to  the  beginner  in  astronomy. 
The  distance  varies  slightly  from  time  to  time  as  its  orbit 
round  our  Earth  is  not  circular,  but  slightly  elliptical  or 
oval ;  but  the  average  distance  is  238,000  miles.  It  is 
near  to  us  when  compared  to  the  other  celestial  bodies.  But 
the  question  at  once  occurs,  How  is  it  possible  to  measure 
the  distance  ?  We  do  not  require  to  reach  the  Moon  in 
order  to  measure  its  distance,  any  more  than  we  require 
to  ascend  a  mountain  to  measure  its  height.  In  these  mea- 
surements we  proceed  on  the  principles  of  land-surveying. 

The  principles  of  land-surveying  depend  on  the 
measurement  of  angles.  As  Professor  Comstock  puts 
it :  "  The  instruments  used  by  astronomers  for  the 
measurement  of  angles  are  usually  provided  with  a  tele- 
scope, which  may  be  pointed  at  different  objects,  and 
with  a  scale  to  measure  the  angle  between  lines  drawn 
from  the  instrument  to  two  different  objects,  such  as  two 
church  steeples,  or  the  Sun  and  Moon,  and  this  is  usually 
called  the  angle  between  the  object.  By  measuring 
angles  iii  this  way  it  is  possible  to  determine  the  distance 
to  an  inaccessible  point.11 

"  An  observer  wishes  to  measure  the  distance  of  a  flag- 
staff at  the  other  side  of  a  river  which  he  is  unable  to 
cross.  Accordingly  he  chooses  two  points  on  his  own 
side  of  the  river,  from  which  to  make  observations.  The 
line  joining  these  points  he  calls  the  base-line,  the  length 
of  which  he  ascertains.  From  either  point  he  measures 
the  angle  "  subtended "  by  the  opposite  sides  at  these 
points.  Having  measured  the  angles,  he  now  determines 
the  elements  of  the  triangle,  and  by  means  of  trigono- 
metry he  knows  the  distance  across  the  river  to  the 
flagstaff  without  having  ever  crossed  it. 

39 


THE   ORB   OF   NIGHT 

Similarly  in  regard  to  the  distance  of  the  Moon.  One 
astronomer  located,  say,  at  Greenwich  or  Edinburgh, 
measures  the  Moon's  position  amid  the  neighbouring  stars. 
Another  at  Cape  Town  or  Sydney,  measures  its  position 
seen  from  that  place.  The  difference  of  position  of  the 
Moon  at  the  two  stations — "  the  parallax  "  as  it  is  called 
— is  then  measured  and  the  distance  of  the  Moon  is 
found  to  be  238,000  miles,  a  great  distance  indeed,  when 
compared  with  our  terrestrial  standards,  but  very  small 
in  the  eyes  of  the  astronomer.  A  railway  train  travelling 
night  and  day  at  the  rate  of  sixty  miles  an  hour  would 
reach  the  Moon  in  six  months.  The  Moon,  as  it  were, 
is  our  own  particular  possession.  It  illuminates  our 
nights ;  it  raises  the  tides  in  our  oceans ;  it  revolves 
around  our  world ;  it  is  the  nearest  of  the  celestial 
bodies,  the  only  one  whose  distance  is  to  be  measured 
in  thousands  of  miles.  As  has  been  remarked,  it  is  a 
detached  continent,  and,  as  we  shall  see  later,  this  is 
probably  true  in  more  senses  than  one.  As  a  result  of 
its  proximity,  we  know  more  of  the  Moon  than  of  any 
other  celestial  body.  Indeed,  we  know  its  geography,  or 
rather  "  selenography,11  better  than  we  know  that  of  the 
Earth.  We  are  close  enough  to  the  Moon  to  see  its 
surface  spread  out  before  us  in  a  bird's-eye  view.  By 
trigonometrical  measurements  we  can  measure  the  heights 
of  the  lunar  mountains.  We  have  seen  the  poles  of  the 
Moon. 

This,  however,  only  applies  to  one  hemisphere  of  the 
Moon.  The  other  side  has  never  been  seen  by  human 
eye.  The  explanation  is  that  the  Moon,  instead  of 
turning  on  its  axis  in  twenty-four  hours  like  the  Earth, 
requires  for  its  rotation  on  its  axis  the  exact  period  of 
its  revolution.  Thus  the  Moon  always  turns  the  same 

40 


THE   ORB   OF   NIGHT 

face  to  the  Earth.  Owing,  however,  to  the  fact  that 
the  Moon's  velocity  in  its  orbit  varies,  the  orbit  being 
slightly  elliptical,  while  the  rate  of  rotation  remains 
the  same,  we  sometimes  catch  a  glimpse  of  the  other 
Direction  from  which  the  Sun's  rays  are  coming. 

»•  i  T   i  •  i 


* 


E 

Various  positions  and  illumination  of  the  Moon  by  the  Sun  during 
her  revolution  around  the  Earth. 


ABCDEFGfl 

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frew        Gvsctnf    First  Quarter  Gibbmu      Full         CiMous    Last  Quarter  Cryscvnl      Artv 

The  corresponding  positions  as  viewed  from  the  Earth,  showing 
the  consequent  phases. 

FIG.  1. — Orbit  and  Phases  of  the  Moon. 

hemisphere.     This  is  known  as  the   "libration"  of  the 
Moon. 

So  far,  the  Moon  has  been  viewed  as  an  object  and  as 
the  satellite  of  the  Earth.  It  must  now  be  considered 
as  a  world.  When  we  look  at  the  Moon,  even  casually, 

41 


THE   ORB   OF  NIGHT 

we  cannot  but  notice  that  the  bright  disc  is  diversified. 
Most  people  see  in  the  full  Moon  a  likeness  to  a  human 
face,  and  this  is  called  "the  Man  in  the  Moon."  Even 
in  the  crescent  Moon  and  half  Moon  it  is  obvious  that 
there  are  dark  markings.  In  early  times  no  one  knew 
what  these  markings  signified.  Some  of  the  ancients 
thought  that  the  Moon  was  a  great  mirror  in  which  we 
saw  the  Earth's  markings  reflected,  while  others  held  the 
correct  view,  namely,  that  the  diverse  markings  repre- 
sented the  actual  configuration  of  the  Moon's  surface. 
Soon  after  the  invention  of  the  telescope,  Galileo  turned 
his  little  instrument  on  the  Moon.  He  was  thus  enabled 
to  show  that  our  satellite  was  diversified  by  mountains 
and  valleys,  and  great  grey  stretches,  which  he  believed 
to  be  seas.  Later  astronomers,  following  in  this  belief, 
gave  these  grey  stretches  names.  Thus  we  have  on  the 
Moon  the  "  Mare  Serenitatis  "— "  Sea  of  Serenity  "  ;  the 
"  Mare  Tranquillitatis  "— "  Sea  of  Tranquillity  "  &c.  It 
was  obvious  as  astronomical  research  progressed  that  these 
stretches  were  not  seas,  but  great  plains.  It  is  now 
known  that  there  are  no  seas  on  the  Moon,  but  the  old 
names  are  retained  for  convenience.  It  is  quite  possible 
that  these  plains  are  ocean  beds,  from  which  the  water 
has  long  since  disappeared. 

Like  the  Earth,  the  Moon  is  diversified  by  all  kinds  of 
formations.  There  are  mountain  ranges,  isolated  moun- 
tains, and  volcanic  craters.  The  mountain  ranges  have 
been  called  after  mountains  on  the  Earth.  Thus  there 
are  on  the  Moon,  the  Alps,  the  Apennines,  and  the 
Carpathians.  The  highest  mountains  on  its  surface,  so 
far  as  known,  are  the  Doerfel  and  Leibnitz  mountains, 
about  25,264  feet  high.  As  Flammarion  remarks : 
"  Relatively  to  its  proportions,  the  satellite  is  much  more 


THE   ORB   OF  NIGHT 

mountainous  than  the  planet,  and  the  mountainous  giants 
are  much  more  numerous  than  here.  If  we  have  peaks 
like  the  highest  of  the  Himalayas,  and  of  the  whole 
Earth,  whose  elevation  of  29,000  feet  is  equivalent  to 
TyVfr  the  diameter  of  our  globe,  there  are  peaks  on  the 
Moon  of  25,264  feet,  those  of  Doerfel  and  Leibnitz,  the 
height  of  which  is  equivalent  to  Ty^  the  lunar  diameter." 
It  will  thus  be  seen  that  the  peaks  of  the  Moon  are  much 
higher  in  proportion  to  its  size  than  those  of  our  own 
world.  The  surface,  too,  is  much  more  rugged  and 
mountainous  than  that  of  the  Earth.  There  has  been 
much  volcanic  activity  on  the  Earth,  but  there  has  been 
much  more  on  the  Moon.  Indeed  on  it  the  volcanic 
crater  is  the  commonest  type  of  formation.  The  smallest 
telescope  will  reveal  the  largest  of  these  wonderful  forma- 
tions. The  craters  are  named  after  eminent  astronomers, 
men  of  science,  and  philosophers,  and  among  the  more 
prominent  are  Tycho,  Copernicus,  Plato,  and  Archimedes. 
Some  of  these  craters  are  enormous.  A  large  type  of 
formations  somewhat  similar  to  the  craters  are  the  walled 
plains.  Some  of  these  are  actually  150  miles  across ; 
and  they  are,  as  their  name  implies,  encircled  by  ram- 
parts of  considerable  breadth,  which  in  some  cases  rise 
to  a  height  of  about  12,000  feet  above  the  enclosed 
plains.  In  some  cases,  too,  the  floors  of  these  walled 
plains  are  diversified  by  the  presence  of  minute  craters 
and  mountains. 

Another  curious  formation  peculiar  to  the  Moon  is 
that  known  as  the  "  rills."  Of  these  rills  the  late  Mr. 
Elger,  a  well-known  English  observer  of  the  Moon, 
writes  :  "  They  often  extend  for  hundreds  of  miles  in 
approximately  straight  lines  over  portions  of  the  Moon^s 
surface,  frequently  traversing  in  their  course  ridges, 

43 


THE   ORB  OF   NIGHT 

craters,  and  even  more  formidable  obstacles,  without  any 
apparent  check  or  interruption.  Their  length  ranges 
from  ten  or  twelve  to  three  hundred  miles  or  more,  their 
breadth  from  less  than  half  a  mile  to  more  than  two, 
and  their  depth  from  a  hundred  to  four  hundred  yards." 
On  the  Earth  we  have  nothing  like  them — great  yawn- 
ing chasms  running  for  miles  over  craters,  mountains, 
and  plains. 

The  study  of  the  Moon's  surface  is  now  a  distinct 
branch  of  astronomy.  To  it  many  distinguished  astro- 
nomers, such  as  Miidler  and  Schmidt,  have  given  the  best 
part  of  their  lives.  Schmidt,  a  notable  German  astro- 
nomer, commenced  his  observations  of  the  Moon,  with  a 
view  to  constructing  a  chart,  at  the  age  of  fourteen.  He 
just  lived  to  finish  his  great  work,  about  forty  years 
later.  In  recent  years  photography  has  been  largely 
used  in  the  study  of  the  Moon,  and  in  the  able  hands 
of  Professor  W.  H.  Pickering  of  Harvard,  U.S.A.,  much 
has  been  learned  in  this  way  concerning  the  lunar  surface. 
To  the  casual  observer  the  first  quarter  is  the  most 
satisfactory  phase.  The  full  Moon  is  a  disappointing 
object  in  the  telescope.  The  Sun  is  shining  direct  on 
its  surface ;  it  is  noon  on  the  part  of  our  satellite  which 
we  are  observing,  and  the  mountains  and  crater  walls 
cast  no  shadows,  just  as  on  our  own  world  the  shadows 
are  shortest  at  noon.  At  the  first  quarter,  on  the  other 
hand,  it  is  positively  fascinating  to  watch  the  dividing 
line  between  light  and  darkness — the  terminator,  as  it 
is  called  in  astronomical  language — and  to  note  the 
sunrise  on  the  various  mountain  peaks.  It  is  about  the 
time  of  the  first  quarter  that  we  see  the  surface  of  the 
Moon  at  its  best.  It  is  at  this  time  that  the  Moon  is 
most  useful  to  the  astronomer,  just  as  the  full  phase 

44 


From  a  photograph  taken  at  the  Paris  Observatory  by  M.  P.  Puise 


THE  MOON 

This  is  a  photograph  taken  near  the  first  quarter,  but,  of  course,  inverted,  as  in 
astronon  ical  telescopes.     The  craters  and  mountain  ranges  are  well  shown. 


THE   ORB   OF   NIGHT 

is  the  most  useful  to  the  ordinary  inhabitant  of  the 
Earth. 

We  have  briefly  described  the  surface  of  the  Moon — its 
grey  plains,  its  mountains,  its  craters,  and  rills.  What 
do  we  learn  from  a  study  of  these  features  ?  Is  our 
satellite  a  world  like  the  Earth  ? 

It  is  not  a  world  like  the  Earth.  The  first  great 
difference  is  obvious  to  the  most  casual  observer.  The 
Moon's  surface  is  always  to  be  seen  clearly  defined  without 
a  trace  of  haziness.  There  is  no  atmosphere.  Practically 
it  is  an  airless  globe.  Could  we  see  the  Earth  from  some 
point  in  space  we  should  sometimes  see  it  clearly  defined 
when  the  atmosphere  was  clear,  but  at  times  we  should 
see  it  enshrouded  in  cloud.  But  we  never  see  clouds  on 
the  Moon  ;  it  is  airless.  Not  only  is  there  no  air.  There 
is  no  water.  The  Moon's  surface  is,  to  all  intents  and 
purposes,  changeless,  airless,  and  lifeless.  Without  air 
there  can  be  no  water,  without  water,  no  life.  There  is 
no  vegetation  on  the  grey  plains,  no  heathery  moors,  no 
pine-covered  mountains,  merely  a  succession  of  arid,  it 
may  be  crumbling  rocks.  As  Professor  W.  H.  Pickering 
has  pointed  out,  there  is  probably  a  certain  amount  of 
change,  almost  imperceptible.  At  the  bottoms  of  the 
craters  there  seem  to  be  some  last  relics  of  the  Moon's 
atmosphere,  and  perhaps  the  remnants  of  a  lunar  vegeta- 
tion, perhaps  a  feeble  little  eruption  almost  unnoticeable, 
but  that  is  all.  The  Moon  is  a  dead  world,  and  it  is 
exceedingly  unlikely — indeed  we  may  say  it  is  impossible 
— that  any  but  the  very  lowest  forms  of  fungus-life  could 
live  on  it  for  one  hour.  The  want  of  air,  as  already 
said,  means  want  of  water ;  it  also  means  violent  change 
of  temperature.  The  Moon's  day  is  equal  to  twenty- 
nine  and  a  half  of  our  days  in  length.  For  half  of  this 

45 


THE   ORB   OF   NIGHT 

period  the  Sun  beats  down  on  the  surface  of  the  Moon. 
There  is  nothing  to  temper  the  broiling  heat.  The  sur- 
face is  scorched  and  baked.  Then  the  Sun  sets,  and  the 
long  night  comes  on.  There  is  no  air  to  retain  the  heat ; 
it  escapes  into  space,  and  the  lunar  surface  is  frozen  by  an 
intense  cold,  a  cold  more  terrible  than  we  can  conceive. 

Could  we  visit  the  Moon,  what  an  extraordinary  world 
we  should  find  it  to  be !  There  is  no  atmosphere,  and 
as  a  consequence  of  this  the  stars  are  visible  in  all  their 
glory  when  the  Sun  is  shining.  On  Earth  the  stars  are 
invisible  in  the  daytime  because  the  sunbeams  are  dis- 
persed in  our  atmosphere,  and  this  "  veil  of  sunbeams " 
hides  the  stars  from  view.  But  on  the  Moon  there  is  no 
veil  of  sunbeams.  The  Sun  is  seen  with  all  his  appendages 
which  on  Earth  are  invisible  except  during  total  eclipses 
— his  red  flames  and  his  corona.  Slowly,  very  slowly, 
the  Sun  creeps  across  the  black  sky,  until  in  fourteen 
earthly  days  he  sinks  below  the  horizon  to  illuminate  the 
opposite  hemisphere. 

From  the  side  of  the  Moon  facing  earthwards,  there 
is  seen  hanging,  fixed  and  motionless  in  the  sky,  an 
enormous  orb,  a  gigantic  moon  shedding  its  rays  con- 
tinually on  the  surface  of  our  satellite.  Sun  and  stars 
may  pass  behind  it,  but  this  orb  hangs  fixed  in  its  place 
in  the  heavens.  This  body,  which  appears  from  thirteen 
to  fourteen  times  as  large  as  the  Moon  seems  to  us,  is 
our  dwelling-place,  the  Earth.  The  magnificence  of  the 
"  Earthlight "  which  our  world  sheds  on  the  surface  of 
the  Moon,  is  difficult  to  imagine.  From  the  Moon's 
surface  our  world  is  to  be  seen  in  all  its  aspects — blue 
skies,  clouded  skies,  haze,  and  mist.  Sometimes  it  is 
"  full  Earth,"  sometimes  "  new  Earth,"  sometimes  the 
quarters,  continually  spinning  on  its  axis,  and  exhibiting 

46 


THE   ORB   OF  NIGHT 

every  part  of  its  surface  in  turn.  Of  the  power  of  this 
reflected  light  we  may  get  an  idea  from  a  consideration 
of  a  common  phenomenon  seen  from  the  Earth.  Most 
people  have  seen  the  "  old  Moon  in  the  new  Moon's 
arms  " — the  crescent  Moon  completed  by  a  darker  portion 
which  shines  with  a  dull  light.  This  is  the  portion  of 
our  satellite  illuminated  by  earthshine  and  reflecting 
back  to  us  the  light  of  our  own  planet.  Thus  we  see 
the  light  of  our  own  world  reflected  back  to  us  from 
the  heavens. 

The  chief  features  of  the  silver  orb  of  night  have  been 
described.  It  has  been  seen  to  be  a  globe,  similar  in  some 
respects  to  the  Earth,  but  vastly  different  in  its  physical 
condition  —  a  globe  uninhabited  and  uninhabitable,  a 
succession  of  rugged,  jagged  rocks,  great  grey  barren 
plains,  and  volcanic  regions.  We  have  now  completed 
our  survey  of  the  Earth's  vicinity,  and  have  passed  the 
first  sign -post  on  a  journey  through  the  depths  of  space. 


CHAPTER   IV 
THE   FOUNTAIN  OF   LIGHT 

SCHIAPARELLI  has  called  the  Sun  "the  most 
magnificent  work  of  the  Almighty,"  and  so  far  as 
our  world  is  concerned  the  orb  of  day  certainly 
merits  the  title.  Without  the  SunfMife  on  the  Earth 
would  be  impossible  ;  without  the  Sun,  indeed,  there  would 
be  no  Earth.  Yet,  so  accustomed  are  Earth's  inhabitants 
to  the  day  star,  that  day  after  day  we  experience  light 
and  heat,  year  after  year  we  enjoy  the  summer  season, 
and  do  not  stop  to  consider  the  source  of  these  marvels. 
It  is  well  to  remember,  occasionally  at  least,  that  the  Sun 
is  all  in  all  to  our  planet. 

There  are  many  marvels  in  connection  with  the  Sun, 
but  perhaps  nothing  is  more  astounding  than  its  vast 
distance  and  enormous  size.  The  distance  of  the  Sun 
from  the  Earth,  as  ascertained  by  methods  similar  to 
those  used  to  measure  the  distance  of  the  Moon — 
mentioned  in  the  previous  chapter — is,  roughly  speaking, 
ninety-three  millions  of  miles.  The  Earth's  orbit  is  not 
exactly  circular,  it  is  slightly  elliptical,  and  as  a  result 
the  Sun's  distance  varies  from  ninety-one  to  ninety-four 
millions  of  miles.  It  is  easy  to  write  out  the  figures 
representing  ninety-three  millions  of  miles  (93,000,000), 
but  it  is  not  so  easy  to  realise  the  enormous  distance  which 
these  figures  represent.  Sir  Robert  Ball  has  given  an 
excellent  illustration  as  follows :  "  How  long  will  the 

48 


THE   FOUNTAIN   OF  LIGHT 

clock  have  to  tick  before  it  has  made  as  many  ticks  as 
there  are  miles  between  the  Earth  and  the  Sun  ?  Every 
minute  the  clock,  of  course,  makes  sixty  ticks,  and  in 
twenty-four  hours  the  total  number  will  reach  86,400. 
By  dividing  this  into  93,000,000  you  will  find  that  more 
than  1076  days,  or  nearly  three  years,  will  be  required  for 
the  clock  to  perform  the  task." 

There  is  another  vivid  way  of  illustrating  the  Sun's  dis- 
tance. A  tour  round  the  world,  involving  a  journey  of 
24,000  miles,  can  be  accomplished  in  sixty  days.  Before 
a  traveller  could  cover  93,000,000  miles  he  would  require 
to  accomplish  about  4000  of  these  journeys.  He  would 
be  six  hundred  years  old  when  he  arrived,  even  supposing 
him  to  start  on  his  journey  as  an  infant.  Take  another 
illustration.  If  it  were  possible  to  travel  to  the  Sun  in 
a  railway  train,  night  and  day  without  stopping,  at  the 
uniform  rate  of  forty  miles  an  hour,  it  would  require  no 
less  than  265  years  to  reach  its  destination.  If  the  train 
had  started  in  the  time  of  Cromwell,  it  would  not  yet 
have  reached  its  destination. 

No  less  astounding  than  the  Sun's  distance  is  its  size. 
The  diameter"  of  the  solar  globe  is  866,000  miles.  No 
fewer  than  109  globes  of  the  size  of  the  Earth  would  be 
necessary  to  stretch  from  the  one  side  of  the  Sun  to  the 
other.  Properly  to  estimate  its  size  in  comparison  with 
that  of  the  Earth,  we  must  consider  its  volume.  The 
volume  of  the  Sun  is  one  and  a  quarter  millions  of  times 
greater  than  the  volume  of  the  Earth.  If  all  the  planets, 
satellites,  and  cometary  and  meteoric  bodies  in  the  solar 
system  were  rolled  into  one  globe,  it  would  take  no  fewer 
than  750  of  such  globes  to  equal  the  volume  of  the 
Sun.  Professor  Gregory  gives  the  following  unique 
illustration  of  the  Sun's  size:  "If  we  had  a  contract 

49  D 


THE   FOUNTAIN   OF  LIGHT 

to  build  up  this  stupendous  bulk,  and  were  to  deliver 
a  load  of  the  same  size  as  the  Earth  every  hour,  the  order 
could  be  completed  working  night  and  day  for  150  years." 
We  have  seen  by  how  much  the  Sun  exceeds  the  Earth 
in  volume.  In  weight,  however,  the  Sun  exceeds  our 
world  only  330,000  times.  This  proves  that  the  density 
of  our  world  is  about  four  times  that  of  the  Sun.  The 
reason  of  this  is  that  while  our  world  is  a  solid  globe,  the 
Sun,  as  we  all  know,  is  a  great  ball  of  gas,  incandescent, 
glowing  with  an  inconceivable  heat.  We  all  feel  that  the 
Sun  is  very  hot ;  even  on  our  planet  it  sometimes  shines 
so  brightly  as  to  make  us  uncomfortable.  What,  then, 
must  be  its  actual  heat  if  it  can  be  oppressive  at  a 
distance  of  93,000,000  miles  ?  Perhaps  the  best  illustra- 
tion on  this  point  was  given  by  Professor  Young,  the 
well-known  American  astronomer :  "  If  we  could  build 
up  a  solid  column  of  ice  from  the  Earth  to  the  Sun 
two  miles  and  a  quarter  in  diameter,  spanning  the  incon- 
ceivable abyss  of  93,000,000  miles,  and  if  the  Sun  should 
concentrate  his  power  upon  it,  it  would  dissolve  and  melt, 
not  in  an  hour,  not  in  a  minute,  but  in  a  single  second ; 
one  swing  of  the  pendulum  and  it  would  be  water,  seven 
more  and  it  would  be  dissipated  in  vapour. "  The 
estimated  temperature  of  the  solar  surface  is  no  less  than 
18,000  degrees  Fahrenheit.  The  heat  emitted  by  the  Sun 
in  each  second,  according  to  one  of  the  most  distinguished 
of  modern  astronomers,  is  equal  to  that  which  would 
result  from  the  combustion  of  eleven  quadrillions,  six 
hundred  thousand  millions  of  tons  of  coal  burning  at 
the  same  time.  This  does  not  help  us  to  realise  the 
heat  of  the  Sun.  It  helps  us  rather  to  realise  how  far 
the  whole  subject  transcends  our  comprehension.  How  is 
this  enormous  heat  maintained  ?  It  has  been  calculated 

50 


PHOTOGRAPH  OF  A  SUNSPOT 

This  fine  picture  was  taken  by  the  late  M.  Janssen.     The  granular  structure  of  the  Sun 
surface  is  here  well  represented.     (From  Knowledge.") 


[    UNIVERSITY    j 


THE   FOUNTAIN    OF  LIGHT 

that  if  the  Sun  were  composed  of  coal  it  would  burn  out 
in  six  thousand  years.  But  the  orb  of  day  has  lasted 
much  longer,  and  seems  to  be  in  its  prime.  The  most 
probable  explanation  of  the  source  of  the  Sun's  heat  is 
that  the  solar  globe  is  contracting.  This  contraction 
generates  heat,  which  it  has  been  calculated  will  keep  the 
Sun  at  a  high  temperature  for  ten  million  years !  It  is 
also  possible  that  the  element  radium  may  have  some- 
thing to  do  with  the  maintenance  of  the  solar  heat,  but 
here  we  are  in  the  region  of  speculation. 

Equally  astounding  is  the  brightness  of  the  Sun.  The 
"intensity  of  sunlight,"  as  it  is  called,  at  the  surface 
has  been  estimated  at  190,000  times  that  of  a  candle 
flame,  146  times  that  of  a  calcium  light,  and  three 
and  two-fifths  that  of  an  electric  arc.  Then  in  regard 
to  the  brightness  of  the  sun,  it  is  estimated  that  the 
total  light  is  equal  to  1,575,000,000,000,000,000,000 
millions  of  wax  candles.  This  unthinkable  row  of  figures 
can  assist  us  in  realising,  as  it  were,  the  incomprehensible- 
ness  of  the  brilliance  of  the  day  star.  In  reference  to  the 
light  and  heat  of  the  Sun,  it  is  well  to  bear  in  mind 
that  the  Earth  and  its  inhabitants  receive  only  a  very 
small  portion.  It  has  been  calculated  that  if  the  Sun 
were  expending,  instead  of  energy,  money  at  the  rate 
of  £1 8,000,000,000  a  year,  the  earth's  annuity  would 
be  only  <£9. 

Owing  to  the  dazzling  brightness  of  the  Sun,  it  is 
impossible  to  observe  it  in  a  telescope  without  the  aid 
of  a  dark  glass.  When  we  first  observe  the  Sun 
through  the  telescope,  we  behold  a  disc  of  yellow 
light.  If  we  scan  the  disc  carefully  we  shall,  in  all 
probability,  notice  one  or  two  minute  markings.  These 
are  the  sunspots.  These  spots  are  not  permanent 

51 


THE  FOUNTAIN   OF  LIGHT 

features  of  the  Sun,  like  the  mountains  and  craters  of 
the  Moon.  They  are  merely  temporary  markings.  Some- 
times, indeed,  they  disappear  in  a  day.  An  astronomer 
looks  at  a  sunspot  carefully  one  day,  and  makes  a 
drawing  of  it.  Next  day  he  looks  for  it  again,  and 
finds  that  it  has  vanished  or  completely  changed  its 
form. 

Now  what  are  these  sunspots  ?  They  were  a  mystery 
to  the  early  astronomers  who  first  discovered  them — 
Galileo  and  Scheiner.  Indeed,  the  discovery  of  these 
spots  came  on  the  men  of  science  of  the  day  with  a 
shock  of  surprise.  It  was  thought  that  the  Sun  was 
too  "  pure  "  to  have  "  defects  "  on  its  surface,  and  accord- 
ingly the  astronomers  who  first  announced  that  they  had 
seen  spots  on  the  Sun,  were  openly  disbelieved.  How- 
ever, the  spots  were  soon  proved  beyond  all  doubt  to 
be  really  features  of  the  disc  of  the  Sun.  Observation  with 
moderate-sized  telescopes,  and  even  with  small  instru- 
ments, reveals  a  very  remarkable  fact  concerning  these 
spots ;  they  are  rents  in  the  glowing  atmosphere  of 
the  Sun.  Another  remarkable  fact  concerning  sunspots 
is  that  they  are  not  uniformly  dark.  The  black  central 
portion — the  umbra,  as  it  is  called — is  surrounded  by 
a  grey  portion — the  penumbra.  These  are  supposed  to 
be  not  really  black  and  grey,  but  merely  dark  in  com- 
parison with  the  brilliant  envelope  of  the  Sun — the 
"  photosphere,"  or  "  light-sphere,"  as  it  is  called.  Spots 
are  supposed  to  be  vast  cavities  in  the  glowing  envelope. 
They  vary  greatly  as  to  size.  Sometimes  a  spot  is  so 
large  as  to  be  visible  to  the  unaided  eye.  One  famous 
spot  was  seen  in  February  1892.  Its  length  was  no  less 
than  92,000  miles,  and  its  breadth  was  62,000  miles.  A 
number  of  small  spots  were  connected  with  the  large  one, 


THE   FOUNTAIN   OF   LIGHT 

and  the  length  of  the  group  was  162,000  miles,  the 
breadth  being  75,000  miles.  The  spot  group  had  an 
area  of  3500  million  square  miles.  Seventy  bodies  equal 
in  size  to  the  Earth  would  have  been  required  to  cover 
up  this  gap  in  the  photosphere.  Most  spots,  how- 
ever, are  by  no  means  so  gigantic  as  was  this  particular 
example. 

Sunspots  reveal  to  astronomers  many  important  facts. 
They  show  that  the  Sun,  like  the  Earth,  rotates  on  its  axis. 
By  observations  of  the  displacements  of  many  spots, 
astronomers  have  found  that  the  rotation  of  the  Sun  is 
performed  in  twenty-five  days  at  the  equator,  and  twenty- 
seven  and  a  half  days  at  forty-five  degrees  north  and 
south  of  the  equator.  That  is  to  say,  the  Sun  does  not 
rotate  as  a  whole.  Different  parts  have  different  periods. 
The  "  day  "  of  the  Sun  therefore  is  over  twenty-five  times 
longer  than  that  of  our  planet. 

Another  remarkable  fact  which  sunspots  reveal  con- 
cerns their  own  distribution.  At  some  seasons  spots  are 
much  more  numerous  than  at  others,  and  it  has  been 
ascertained  that  they  increase  and  decrease  in  about  every 
eleven  years.  Thus  1889  and  1901  were  years  of  few 
sunspots,  while  1893  and  1905  were  years  of  many  spots. 
The  history  of  the  discovery  of  the  "  solar  cycle,"  as  this  in- 
crease and  decrease  is  called,  is  one  of  the  most  interesting 
in  the  annals  of  astronomy.  In  1826  a  German  apothe- 
cary named  Schwabe,  who  was  interested  in  the  study 
of  astronomy,  commenced  to  count  the  number  of  spots 
on  the  Sun  from  day  to  day.  His  only  instrument  was 
a  small  hand  telescope.  After  about  twenty  years  he 
found  traces  of  the  increase  and  decrease,  and  by  1851 
had  fully  proved  the  existence  of  the  "  sunspot  period." 
Here  was  a  discovery  which  had  escaped  all  the  great 

53 


THE   FOUNTAIN   OF   LIGHT 

astronomers,  and  fell  to  be  made  by  an  amateur.  Besides 
the  spots,  the  telescope  reveals  the  existence  of  bright 
ridges  which  are  known  as  "  faculae."  These  are  usually 
observed  close  to  the  spots.  Like  them,  they  are  far 
from  being  permanent  features.  Even  in  a  few  hours 
they  utterly  change  their  shape,  and  in  some  cases  it 
is  impossible  to  sketch  their  form,  so  quickly  do  they 
alter  and  disappear.  Although  they  are  closely  con- 
nected with  spots,  there  is  one  remarkable  difference. 
Spots  are  usually  confined  to  two  zones  above  and  below 
the  solar  equator,  while  faculae  are  found  in  every 
latitude,  except  in  the  polar  regions. 

It  is  important  to  remember  that  the  greater  part  of 
our  knowledge  of  the  Sun  has  been  derived  from  obser- 
vations not  with  the  telescope  alone,  but  with  the  tele- 
scope aided  by  an  instrument  even  more  remarkable. 
This  instrument  is  called  the  spectroscope,  and  in  order 
to  understand  properly  many  of  the  latest  and  most 
wonderful  discoveries  in  astronomy,  it  is  necessary  to 
have  some  idea  of  the  principle  of  this  instrument.  Put 
briefly,  it  may  be  said  that  while  the  telescope  reveals 
the  celestial  bodies,  the  spectroscope  tells  us  the  materials 
of  which  they  are  composed.  Just  as  water  can  be  broken 
up  into  its  elements,  oxygen  and  hydrogen,  sunlight  can 
be  broken  up  into  its  primary  colours,  red,  orange,  yellow, 
green,  blue,  indigo,  and  violet.  This  can  be  done  by 
passing  sunlight  through  a  prism  of  glass,  and  the  strip 
of  rainbow-coloured  light  which  results  is  called  the  solar 
spectrum.  In  fact  the  rainbow  is  merely  the  solar 
spectrum  produced  naturally  by  what  is  known  as  re- 
fraction, the  bending  or  deflection  of  the  rays  of  the 
Sun.  The  solar  spectrum  was  first  investigated  by  Sir 
Isaac  Newton,  but  it  was  not  until  the  year  1814  that 

54 


THE   FOUNTAIN   OF   LIGHT 

Fraunhofer,  a  German  astronomer,  noticed  in  the  spectrum 
a  number  of  dark  lines.  He  detected  about  three  or  four 
hundred  of  these,  and  named  the  more  prominent  by  the 
letters  of  the  alphabet  from  A  in  the  red  to  H  in  the 
violet.  He  was  greatly  perplexed  at  first  over  the  mean- 
ing of  the  lines.  He  found  that  they  were  conspicuous  in 
the  spectra  shown  by  the  Moon  and  planets,  but  not  in 
the  spectra  of  all  the  stars.  In  other  words,  the  lines  were 
found  to  be  characteristic  of  sunlight,  whether  direct  or 
reflected,  and  sunlight  only.  It  is  possible,  however,  to 
analyse  other  kinds  of  light  besides  sunlight.  In  a 
physical  laboratory  the  lights  of  heated  elements  may 
be  observed  with  the  spectroscope,  an  elaborated  form 
of  the  ordinary  prism,  and  when  each  element  is  thus 
analysed  it  is  found  to  be  characterised  by  one  or  more 
bright  lines.  In  1859,  Kirchhoff,  a  German  scientist, 
showed  that  while  a  gaseous  substance  gives  a  spectrum 
of  bright  lines,  a  luminous  solid,  or  liquid,  gives  a  con- 
tinuous spectrum.  In  the  words  of  a  lucid  astronomical 
writer,  "  substances  of  every  kind  are  opaque  to  the  pre- 
cise rays  which  they  emit.  That  is  to  say,  they  stop  the 
kinds  of  light  or  heat  which  they  are  then  actually  in 
a  condition  to  radiate.11  This  was  the  solution  of  the 
problem.  All  that  astronomers  had  to  do  was  to 
examine  the  spectra  of  heated  elements  and  fix  the 
position  of  the  bright  lines  in  these  spectra,  and 
afterwards  compare  the  position  of  these  lines  with 
the  position  of  the  dark  lines  in  the  spectrum  of  the 
Sun.  As  the  positions  were  in  many  cases  identical,  it 
became  possible  to  ascertain  of  what  substances  the  Sun 
was  composed,  and  Kirchhoff  was  enabled  to  detect  the 
presence  in  the  orb  of  day  of  such  well-known  elements 
as  sodium,  iron,  copper,  zinc,  and  magnesium. 

55 


THE   FOUNTAIN    OF   LIGHT 

One  of  the  uses  of  the  spectroscope  is  to  determine  the 
elements  of  the  Sun ;  but  it  has  other  uses.  It  has  dis- 
closed to  astronomers  the  existence  of  another  atmos- 
phere. In  the  chapter  on  eclipses  of  the  Sun,  mention 
will  be  made  of  two  solar  features  which  are  then  seen  to 
full  advantage.  These  are  the  red  flames  or  prominences, 
and  the  corona,  a  halo  of  silvery  light.  We  do  not  see 
these  features  of  the  Sun  every  day,  because  they  are 
obscured  by  its  dazzling  luminosity.  When,  however, 
the  dark  globe  of  the  Moon  interposes  and  cuts  off'  the 
light  of  the  photosphere,  they  are  visible.  By  means  of 
the  spectroscope  it  is  possible,  however,  to  observe  the 
prominences  daily,  and  consequently  our  knowledge  of 
these  marvellous  objects  has  greatly  increased  since  the 
application  to  them  of  this  instrument.  They  have  been 
ascertained  to  be  tongues  of  glowing  hydrogen  shot  forth 
with  tremendous  power  from  the  chromosphere,  a  thin 
layer  surrounding  the  photosphere.  Some  of  these  pro- 
minences are  enormous  in  height.  An  extraordinary 
outburst  was  witnessed  on  September  7,  1871,  by  the 
late  Professor  Young,  one  of  the  foremost  solar  observers. 
At  noon  he  was  examining  a  prominence  by  the  spectro- 
scope method.  "  It  had  remained  unchanged  since  noon 
of  the  day  previously — a  long,  low,  quiet-looking  cloud, 
not  very  dense,  or  brilliant,  or  in  any  way  remarkable 
except  for  its  size.11  At  12.30  A.M.  the  Professor  left 
the  spectroscope  for  a  short  time,  and  on  returning  half- 
an-hour  later  to  his  observations,  he  was  astonished  to 
find  the  gigantic  Sun  flame  shattered  to  pieces.  The 
solar  atmosphere  "  was  filled  with  flying  d£bris?  and  some 
of  these  portions  reached  a  height  of  100,000  miles  above 
the  solar  surface.  Moving  with  a  velocity  which,  even  at 
the  distance  of  93,000,000  miles,  was  almost  perceptible 

56 


THE   FOUNTAIN   OF   LIGHT 

to  the  eye,  these  fragments  doubled  their  height  in  ten 
minutes.  On  January  30,  1885,  another  distinguished 
solar  observer,  the  late  Professor  Tacchini  of  Rome, 
observed  one  of  the  greatest  prominences  ever  seen  by 
man.  Its  height  was  no  less  than  142,000  miles — 
eighteen  times  the  diameter  of  the  Earth.  Another 
mighty  flame  was  so  vast  that  supposing  the  eight  large 
planets  of  the  solar  system  ranged  one  on  the  top  of 
the  other,  the  prominence  would  still  tower  above  them. 

Like  the  spots,  the  prominences  increase  and  decrease 
every  eleven  years.  The  law  which  governs  the  number 
and  distribution  of  the  spots  also  governs  the  prominences. 
This  eleven-year  period  governs  more  than  prominences 
and  spots.  It  also  governs  the  shape  of  the  corona,  a 
silvery  radiance  which  envelops  the  Sun  outside  of  the 
chromosphere.  The  entire  Sun  is  governed  by  this  period, 
which  as  a  result  influences  the  other  bodies  of  the  solar 
system.  Take  the  magnetic  variations  on  the  Earth. 
These  magnetic  variations  indicate  a  period  of  almost 
eleven  years.  Not  only  the  periods  agree,  but  a  great 
outburst  of  spots  and  prominences  on  the  Sun  is  usually 
answered  by  a  magnetic  outbreak  on  the  Earth.  In 
February,  1892,  a  large  group  of  sunspots  appeared,  and 
the  result  was  great  disturbances  of  the  delicate  magnetic 
needles  kept  at  Greenwich  and  elsewhere.  In  February, 
1907,  another  great  group  appeared.  It  was  followed  by 
a  magnificent  display  of  the  Aurora  Borealis,  or  Northern 
Lights,  an  electrical  phenomenon  which  is  caused  by 
electrical  discharges  in  the  upper  regions  of  the  Earth's 
atmosphere.  As  Professor  Gregory  remarks :  "  Mag- 
netic storms  are  generally  accompanied  by  auroral  dis- 
plays, and  vice  versa.  What  is  more,  the  frequency  of 
auroras  keeps  time  with  the  frequency  of  sunspots,  and 

57 


THE  FOUNTAIN   OF  LIGHT 

therefore  with  the  intensity  and  magnitude  of  magnetic 
variations."  In  a  word,  the  Sun  is  the  pulse  of  the  solar 
system,  from  which  all  influences  run  outward. 

We  may  now  briefly  review  what  is  known  of  the 
constitution  of  the  Sun.  The  central  portion  of  the 
mighty  orb  below  the  photosphere  has  never  been  seen. 
In  the  words  of  an  able  writer,  "  Of  the  heat  in  the  Sun's 
interior  we  can  form  no  conception.  The  pressure  within 
the  Sun  is  equally  inconceivable.  A  cannon  ball  weighing 
100  Ib.  on  Earth  would  weigh  2700  on  the  Sun.  Thus 
a  mighty  conflict  goes  on  unceasingly  between  imprisoned 
and  expanding  gases  and  vapours  struggling  to  burst  out, 
and  massive  pressures  holding  them  down." 

The  first  solar  envelope  is  the  photosphere,  that  bright 
calm -looking  solar  surface  on  which  the  spots  appear  and 
from  which  we  derive  our  light.  Above  this  are  envelopes 
technically  known  as  "the  reversing  layer""  and  the 
chromosphere.  This  latter  envelope,  from  which  the 
prominences  emanate,  may  be  described  as  a  sea  of  fire, 
in  a  state  of  everlasting  turmoil  and  unthinkable  heat. 
Like  the  sea,  it  is  restless  and  agitated,  but  its  waves  are 
waves  of  glowing  hydrogen,  and  its  spray  fragments  of 
shattered  sun-flames.  Beyond  the  chromosphere  is  the 
corona,  a  soft  silvery  radiance,  which  can  only  be  seen 
when  the  Sun  is  totally  eclipsed.  The  corona  has  long 
proved  a  problem  to  astronomers.  Its  shape  varies  in 
sympathy  with  the  eleven-year  period,  and  it  seems 
closely  connected  with  electricity  and  magnetism.  It 
streams  out  from  the  Sun  for  millions  of  miles,  becoming 
more  and  more  rarefied  until  it  gradually  fades  into  the 
ether  of  space.  It  is  the  final  solar  envelope,  calm  and 
peaceful,  a  fitting  crown  for  the  orb  of  day. 

This,  then,  is  the  Sun — ruler  and  centre  of  the  Solar 

58 


THE   FOUNTAIN   OF  LIGHT 

System,  to  which  we  on  Earth  owe  our  light,  heat,  life. 
We  cannot  hope  to  realise  fully  the  marvels  of  this 
mighty  orb,  or  properly  to  appreciate  the  delicate 
mechanism,  the  marvellous  contrivances  which  keep  the 
grand  central  orb  in  touch  with  the  little  planets  which 
circle  round  it.  Without  the  Sun,  not  only  would  life 
on  this  planet  be  impossible,  but  our  planet  itself  would 
not  be  in  existence.  In  view  of  all  this  we  can  fully 
appreciate  the  remark  of  Proctor :  "  If  there  is  any 
object  which  men  can  properly  take  as  an  emblem  of 
the  power  and  goodness  of  Almighty  God,  it  is  the  Sun." 


59 


A 


CHAPTER   V 

THE   SUN'S   FAMILY   OF   WORLDS 

STUDY  of  the  globe  of  the  Sun  itself  gives  us  an 
inadequate  idea  of  the  solar  power.  We  cannot 
realise  the  extent  of  the  Sun's  influence  until  we 
comprehend  the  marvellous  system  of  planets  and  satel- 
lites, asteroids,  comets,  and  meteors  which  revolve  round 
it.  The  Sun,  as  has  been  well  said,  "  maintains  in  his 
rays  the  whole  of  his  system.  If  the  comparison  were  not 
offensive  to  the  Sun-god,  we  might  say  that  he  is  like  a 
spider  at  the  centre  of  his  web.  In  the  net  of  his  attraction 
the  worlds  are  sustained.  Relatively  to  his  magnitude 
and  might,  the  planets  are  but  toys  spinning  round  him." 
The  planets  are  divided  into  three  well-defined  groups. 
Comparatively  close  to  the  orb  of  day,  at  mean  distances 
ranging  from  36  to  141  millions  of  miles,  revolve  the  inner 
planets,  consisting  of  four  worlds — Mercury,  Venus,  the 
Earth,  and  Mars.  Beyond  the  orbit  of  Mars  we  have 
another  group,  or  rather  ring,  of  seven  hundred  small 
worlds,  the  asteroids,  planetoids,  or  minor  planets.  The 
largest  of  these  is  only  five  hundred  miles  in  diameter. 
Beyond  this,  at  mean  distances  ranging  from  482  to  2789 
millions  of  miles,  we  have  the  group  known  as  the  outer 
planets — Jupiter,  Saturn,  Uranus,  and  Neptune.  Mere 
figures  convey  little  or  no  idea  of  the  relative  distances  of 
the  planets.  We  may,  however,  represent  the  sizes  and 
distances  of  the  planets  in  imagination  on  a  much  smaller 
scale. 

60 


THE   SUN'S   FAMILY   OF  WORLDS 

If  we  take  a  nine-foot  globe  to  represent  the  Sun,  we 
may  represent  Mercury  by  a  large  pea  at  a  distance  of 
127  yards ;  Venus  by  a  one-inch  ball  at  235  yards ;  the 
Earth  by  a  one-inch  ball  at  325  yards ;  Mars  by  a  half- 
inch  marble  at  495  yards,  the  asteroids  by  700  small  seeds 
at  distances  of  from  676  to  1385  yards.  Jupiter  will  be 
represented  by  an  eleven-inch  globe  a  mile  away  ;  Saturn 
by  a  nine-inch  globe  1  f  miles  away ;  Uranus  by  a  four- 
inch  globe  5 1  miles  away.  On  this  same  scale  we  can 
represent  the  Moon  as  a  pea  moving  in  a  circle  at  a 
distance  of  30  inches  from  the  ball,  one  inch  in  diameter, 
which  represents  the  Earth.  The  actual  diameters  of  the 
planets  may  be  tabulated  as  follows : — 

Inner  planets. — Mercury       ....  3030  miles 

„         „  Venus 7700     „ 

„          „  The  Earth    ....  7918     „ 

„          „  Mars 4230    „ 

The  Asteroids. —From  500  to  10  miles 

Outer  planets. — Jupiter        ....  92,164  miles 

Saturn          ....  74,000    „ 

„          „  Uranus         ....  31,000     „ 

„          „  Neptune       ....  34,000     „ 

From  this  table  we  see  that  the  outer  planets  greatly 
exceed  in  size  the  inner  planets,  which  in  their  turn  dwarf 
to  complete  insignificance  the  asteroids  or  minor  planets. 
The  three  groups,  in  fact,  are  completely  different  in 
distance,  size,  and  physical  condition. 

Besides  the  planets,  another  class  of  bodies  fall  to  be 
mentioned.  The  planets  themselves,  which  revolve  directly 
round  the  sun,  are  called  primary  planets.  But  most 
of  the  planets  are  themselves  centres  of  little  families  of 
moons  or  satellites  which  revolve  round  them  and  are 
carried  along  with  them  round  the  Sun.  These  are  called 
secondary  planets,  or,  more  usually,  satellites.  Mercury 

61 


THE   SUN'S   FAMILY  OF  WORLDS 

and  Venus  have  no  satellites,  and  only  two  of  the  inner 
planets  are  attended  by  moons.  We  all  know  the  Moon, 
the  Earth's  sole  satellite  world.  Mars  has  two  satellites, 
but  they  are  very  much  smaller  than  the  Moon.  The 
asteroids,  of  course,  have  no  satellites,  because  they  are 
much  smaller  than  satellites  themselves.  But  the  outer 
planets  have  imposing  retinues  of  attendants.  Jupiter 
boasts  of  no  fewer  than  eight,  four  large  and  four  small. 
Saturn  is  attended  by  ten  worlds,  and  in  addition  has  a 
ring  of  meteoric  particles  somewhat  analogous  to  the  zone 
of  asteroids  moving  round  the  Sun.  Uranus  has  four 
satellites,  and  Neptune,  so  far  as  we  know  at  present,  one. 
These  satellites  vary  greatly  in  size,  from  Titan,  one  of  the 
satellites  of  Saturn,  which  exceeds  the  planet  Mercury  in 
size,  to  the  little  satellites  of  Mars,  which  are  certainly 
under  thirty  miles  in  diameter.  The  orbits  or  pathways 
of  the  various  planets  round  the  Sun  lie  almost  in  the 
same  plane  or  level,  with  the  exception  of  the  orbits  of 
some  of  the  asteroids.  Along  these  orbits  the  planets 
travel  with  different  velocities. 

Mercury 


V*rm« 

21 

* 

Tb«  TCflrt.li 

18 

Mars 

15 

.Tnpit.pr 

8 

' 

Saturn. 

« 

Uranus 

4 

Neptune. 

* 

FIG.  2.— Comparative  Velocities  of  the  Planets. 

Mercury,  the  nearest  planet  to  the  Sun,  is  subjected  most  to 
the  Sun's  attraction,  and  consequently  travels  fastest.  Its 
velocity  is  twenty-nine  miles  per  second,  or  2,505,000 
miles  per  day.  Venus  travels  at  over  twenty-one  miles 
per  second,  or  1,873,000  miles  per  day.  The  velocity  of 

62 


THE   SUN'S  FAMILY  OF  WORLDS 

our  own  planet  is  eighteen  miles  per  second,  or  1,555,000 
miles  per  day.  Mars  travels  at  almost  fifteen  miles  per 
second,  which  is  equivalent  to  1,287,000  miles  a  day. 

The  outer  planets  are  more  leisurely.  Jupiter  glides 
along  at  eight  miles  a  second,  or  771,000  miles  a  day. 
Saturn's  velocity  is  over  six  miles  per  second,  which  is 
equivalent  to  536,000  miles  a  day.  Uranus  travels  at  a 
little  over  four  miles  a  second,  and  in  one  day  covers 
372,000  miles,  while  Neptune,  the  most  distant  known 
world,  moves  at  the  comparatively  slow  pace  of  three 
miles  a  second,  or  268,000  miles  a  day.  Comparatively 
slow  in  comparison  with  the  other  planets,  but  absolutely 
very  fast,  Neptune  rushes  along  in  its  orbit  with  an 
almost  inconceivable  velocity.  And  if  Neptune's  speed  is 
so  great  that  it  cannot  be  realised,  it  is  almost  impossible 
to  conceive  that  our  world,  which  seems  to  us  so  still  and 
immovable,  carries  us  along  with  it  in  its  journey  through 
space  at  the  rate  of  eighteen  miles  per  second  and  Mercury 
at  twenty-nine  miles  per  second.  The  following  words  of 
Flammarion  bring  out  this  clearly  :  "  A  ball  fired  from  a 
cannon  leaves  the  mouth  with  a  velocity  of  1312  feet  per 
second,  the  terrestrial  globe  flies  75  times  quicker,  Mercury 
117  times  .faster.  This  is  a  rapidity  so  stupendous  that 
if  two  planets  were  to  meet  in  their  course  the  shock 
would  be  frightful ;  not  only  would  they  be  shattered  in 
pieces,  both  reduced  to  powder,  but  further,  their  motion 
being  transformed  into  heat  they  would  be  suddenly 
raised  to  such  a  degree  of  temperature  that  they  would 
disappear  in  vapour — everything,  earth,  stones,  water, 
plants,  inhabitants — and  they  would  form  an  immense 
nebula."  Fortunately  we  need  have  no  apprehension  of 
such  a  disaster.  The  planets  are  all  moving  in  the  same 
direction  and  they  are  at  enormous  distances  from  one 

63 


THE   SUN'S  FAMILY   OF  WORLDS 

another.  When  Mars  and  the  Earth  are  at  their  nearest 
approach,  over  thirty  millions  of  miles  separate  them, 
while  Venus,  the  nearest  of  all  the  large  planets,  is 
distant  from  us  at  its  times  of  closest  approach  over 
twenty  millions  of  miles. 

As  a  result  of  these  different  speeds  and  different 
distances  from  the  central  orb  of  the  various  planets,  the 
various  bodies  of  the  solar  system  require  different  times 
to  perform  their  revolution  round  the  Sun.  Not  only  is 
Mercury  closer  to  the  Sun  than  is  our  own  planet,  and 
has  therefore  a  smaller  ellipse  to  traverse ;  it  goes  much 
more  rapidly  round  its  orbit,  and  therefore  requires  a 
much  shorter  period  to  perform  a  complete  revolution. 

The  times  of  revolution  of  the  various  planets  round 
the  Sun  may  be  tabulated  thus : — 

Mercury  ....  88  days 

Venus  ....  225  „ 

The  Earth  ...  365  „ 

Mars  ....  687  „ 

Jupiter  ....  4332  „    (almost  12  years) 

Saturn  ....  10,759  „     (almost  30  years) 

Uranus  ....  30,687  „     (about  84  years) 

Neptune  ....  60,127  „     (about  165  years) 

Just  as  the  Earth's  year  is  its  period  of  revolution 
round  the  Sun,  the  year  of  Mercury  is  only  88  days, 
while  that  of  Neptune  is  60,127  of  our  terrestrial  days, 
or  almost  1 65  of  our  own  terrestrial  years.  Thus,  a  being 
who  had  lived  only  twenty-four  terrestrial  years  would 
be  a  centenarian  on  Mercury,  while  a  man  of  eighty-four 
on  our  planet  would  be  an  infant  of  one  year  according 
to  the  length  of  years  on  the  planet  Uranus.  In  the  Solar 
\System,  therefore,  measurement  of  time  is  relative  and  de- 
pends on  the  distances  of  the  various  planets  from  the  Sun. 

64 


THE  VARYING  FORCE  OF  GRAVITY  ON  THE  DIFFERENT  PLANETS 

An  athlete  on  the  Moon  could  jump,  with  the  same  exertion,  six  times  as  high 
as  on  the  Earth  ;  on  Jupiter  he  could  only  jump  .j^s  times  as  high.  In  the  centre 
is  a  normal  jump  on  the  Earth  ;  to  the  right  a  jump  on  the  Moon  ;  to  the  left  a 


THE   SUN'S  FAMILY   OF   WORLDS 

As  the  different  planets  vary  in  distance,  velocity, 
and  size,  they  also  differ  in  weight.  Professor  Gregory 
gives  the  weight  of  the  Earth  as  6000  millions  of  millions 
of  tons.  If  we  represent  this  by  one  pound,  the  weight 
of  the  Sun  would  be  150  tons  ;  the  weight  of  Jupiter 
would  be  310  pounds  ;  of  Saturn  93  pounds  ;  of  Neptune 
17  pounds ;  and  of  Uranus  14  pounds.  The  smaller 
planets,  however,  would  be  on  the  same  scale,  lighter  than 
the  Earth.  Venus  would  weigh  13  ounces,  Mars  1^  ounces, 
Mercury  1  ounce,  and  the  Moon  about  3  drams.  Although 
the  outer  planets  are  much  heavier  than  the  Earth,  they 
are  not  so  much  heavier  as  they  are  larger,  which  shows 
that  their  density  is  less  than  that  of  the  Earth. 

On  the  Earth  a  falling  body  during  the  first  second 
of  its  descent,  falls  through  16  feet.  The  following  are 
the  distances  through  which  a  similar  body  would  fall  on 
the  other  bodies  of  the  solar  system  in  the  same  time : — 

Earth   Moon  Mercury  Venus  Mars  Jupiter  Saturn  Uranus  Neptune 


j 

26ft. 

6'] 

ft. 

6-9  ft. 

10-8  ft. 

• 

14-2  ft 

13-1  ft. 

1G 

ft. 

18-9  ft. 


FIG.  3. — Surface-Gravity  on 
the  various  Planets. 


42-4  ft. 


65 


THE   SUN'S   FAMILY  OF   WORLDS 

On  the  same  scale  the  distance  fallen  on  the  Sun  is  too 
large  to  be  shown — 442 '4  feet. 

The  weight  of  the  body  at  the  Earth's  surface  is  the 
force  with  which  the  Earth  attracts  that  body  and 
depends  on  the  mass  of  the  Earth.  Therefore,  as  the 
planets  have  different  masses,  a  body  if  weighed  on  the 
different  planets  would  have  different  weights.  Take  the 
case  of  a  man  who  weighs  twelve  stones  on  the  Earth.  On 
the  Sun  he  would  weigh  two  tons.  As  Sir  Robert  Ball 
puts  it,  if  a  man  were  to  be  transferred  to  a  globe  as 
massive  as  the  Sun,  everything  would  weigh  twenty-seven 
times  as  much  as  it  does  on  the  Earth.  "  To  pull  out 
your  watch  would  be  to  hoist  a  weight  of  about  five  or  six 
pounds  out  of  your  pocket.  Indeed  I  do  not  see  how 
you  could  draw  out  your  watch,  for  even  to  raise  your 
arm  would  be  impossible — it  would  feel  heavier  by  far 
than  if  it  were  made  of  solid  lead.  It  is,  perhaps,  con- 
ceivable that  you  might  stand  upright  for  a  moment, 
particularly  if  you  had  a  wall  to  lean  up  against,  but 
of  this  I  feel  certain  that  if  you  once  got  down  to  the 
ground,  it  would  be  utterly  out  of  your  power  to  rise 
again."  Thus,  a  man  living  on  such  a  globe  would  be 
unable  to  rise  out  of  his  bed  in  the  morning. 

A  man  weighing  12  stone  on  our  world  would  weigh 
28  stone  on  Jupiter,  14  stone  on  Saturn,  10  stone  on 
Neptune,  Uranus,  and  Venus.  On  Mars  and  Mercury 
the  weight  would  be  reduced  to  5  stone,  on  the  Moon 
to  2,  while  on  the  asteroids  it  would  come  down  to  a  few 
ounces.  Let  us  suppose  a  man  of  12  stone  placed  on  the 
Moon.  He  would  be  amazed  to  find  everything  one-sixth 
as  heavy  as  on  the  Earth.  His  own  weight  would  be  so 
diminished  that  he  could  jump  over  a  house  with  as  little 
effort  as  he  could  on  Earth  leap  across  a  wayside  ditch. 

66 


THE   SUN'S   FAMILY   OF  WORLDS 

Pulling  out  his  watch  he  would  feel  practically  no  weight 
at  all.  A  horseman  who  on  Earth  would  consider  a  five- 
barred  gate  a  good  jump,  would  on  the  Moon  leap  over 
a  hayrick  with  the  same  amount  of  exertion.  Suppose  a 
man  were  playing  cricket  on  the  Moon.  On  Earth 
100  yards  is  a  very  good  throw ;  on  the  Moon  one  of 
600  yards  would  be  accomplished  with  the  same  amount 
of  exertion.  One  able  astronomer  puts  this  lessened 
gravity  very  clearly  : — "  Football  would  show  a  striking 
development  in  lunar  play ;  a  good  kick  would  not  only 
send  the  ball  over  the  cross-bar,  but  it  would  go  soaring 
over  the  houses  and  perhaps  drop  in  the  next  parish." 

If  our  imaginary  man  of  twelve  stones  weight  were 
transferred  to  one  of  the  asteroids  which  circulate  be- 
tween Mars  and  Jupiter,  his  weight  would  be  reduced  to  a 
few  ounces.  Suppose  he  kicked  a  ball  into  the  air  as  an 
ordinary  player  would  do  on  Earth,  it  would  not,  as  in 
the  Moon,  go  soaring  over  the  houses  ;  it  would  go  soaring 
into  space  and  leave  the  planet  for  ever.  The  force  of 
gravity  on  the  little  asteroid  would  not  be  sufficient  to 
counteract  the  upward  motion  of  the  ball,  which  would 
rush  into  space  on  a  career  of  its  own,  and  become  a  little 
asteroid  on  its  own  account.  These  illustrations  bring 
home  clearly  the  different  masses  of  the  various  planets 
composing  the  solar  system. 

For  reasons  which  will  be  explained  later,  the  planets 
have  different  densities.  Thus  Mercury  is  in  proportion 
to  its  size  a  very  heavy  planet.  Its  density  is  equal 
to  that  of  zinc,  which  means  that  it  weighs  the  same 
as  a  globe  of  zinc  the  same  size.  The  weight  of  our 
Earth  is  equal  to  that  of  a  globe  of  arsenic  the  same  size. 
The  densities  of  the  other  bodies  of  the  solar  system  vary 
considerably.  That  of  Venus  is  equal  to  iron  pyrites, 

67 


THE   SUN'S  FAMILY   OF  WORLDS 

that  of  Mars  to  ruby,  and  that  of  the  Moon  to  flint-glass. 
The  Sun  and  the  four  large  planets,  although  so  much 
superior  to  the  inner  planets  in  size,  have  smaller  densities. 
The  Sun  and  Jupiter  weigh  the  same  as  globes  of  dry 
sand  the  same  size,  while  the  densities  of  Uranus,  Neptune, 
and  Saturn  are  equal  to  those  of  amber,  boxwood,  and 
walnut-wood. 

The  key  to  the  different  velocities,  densities,  and  masses 
of  the  planets  is  the  marvellous  power  of  gravitation, 
which  was  referred  to  in  the  opening  chapter,  and  the 
complete  investigation  of  which  we  owe  to  the  genius  of 
Newton.  Not  only  the  planets  and  their  satellites,  but 
the  various  comets  and  the  systems  of  meteoric  rings  con- 
form to  this  mighty  law  which  extends  throughout  the 
entire  length  and  breadth  of  the  Universe.  Gravitation 
is  the  marvellous  invisible  bond  everywhere  present, 
operating  throughout  all  space,  which  keeps  the  planets 
in  subjection  to  the  Sun,  and  which  maintains  order 
instead  of  chaos,  harmony  instead  of  discordance.  Much 
as  astronomers  know  of  the  operation  of  gravitation,  of  its 
nature  they  are  entirely  ignorant.  In  contemplating  this 
marvellous  force  which  so  far  has  baffled  science,  the  mind 
is  lifted  right  into  the  region  of  things  Divine  and  Eternal. 

In  this  chapter  we  have  briefly  referred  to  the  system 
of  planets  surrounding  the  Sun.  The  solar  system  is  not 
only  a  system,  but  a  system  of  systems,  for,  as  we  have 
seen,  the  various  planets  with  their  satellites  form  sub- 
ordinate systems  within  the  larger  one.  To  explain  the 
outstanding  features  of  these  planets  and  satellites  will 
be  the  task  of  the  next  few  chapters. 


68 


CHAPTER  VI 

MERCURY— "THE  SPARKLING   ONE" 

SO  far  as  we  know,  Mercury  is  the  nearest  planet  to 
the  Sun.  The  existence  of  a  world  at  a  less  distance 
than  Mercury  was  suspected,  and  indeed  generally 
believed  in,  half  a  century  ago.  There  were  certain  irre- 
gularities in  the  motion  of  Mercury  which  astronomers 
attributed  to  the  action  of  an  unseen  planet.  One  ob- 
server boldly  announced  that  he  had  seen  the  planet 
crossing  in  front  of  the  Sun,  and  so  the  name  of  Vulcan 
was  bestowed  on  the  supposed  world.  But  Vulcan  was 
never  seen  again,  and  accordingly  the  great  majority  of 
astronomers  believe  that  it  never  was  seen — in  fact,  that 
no  such  planet  exists. 

Mercury,  therefore,  is  the  nearest  known  planet  to  the 
Sun.  Seen  from  the  Earth,  the  little  orb  is  never  far 
from  the  day  star.  Mercury  revolves  round  the  Sun  in 
an  orbit  within  that  of  the  Earth,  and  consequently  it  is 
never  to  be  seen  on  a  dark  sky  in  the  opposite  part  of  the 
heavens  to  the  Sun.  In  Britain,  Mercury  is  rarely  visible, 
so  close  does  it  keep  to  the  orb  of  day.  In  fact,  it  is 
recorded  of  Copernicus,  to  whom  we  owe  the  true  theory 
of  the  planetary  motions,  that  although  he  often  looked 
for  the  planet,  he  was  never  successful  in  seeing  it.  The 
reason  of  his  failure  is  not  far  to  seek.  He  lived  the 
greater  part  of  his  life  near  the  valley  of  the  Vistula,  in 
Poland,  where  the  horizon  is  rarely  free  from  mists,  and 

69 


MERCURY— "THE  SPARKLING  ONE" 

Mercury  is  never  very  far  above  the  horizon.  Notwith- 
standing the  difficulty  of  seeing  it,  Mercury  has  been 
known  from  the  earliest  times.  The  ancient  Greeks 
were  well  acquainted  with  it,  and  it  was  sometimes  known 
to  them  as  the  "  sparkling  one."  This  name  was  given 
to  it  because  it  does  not,  like  the  other  planets  which  rise 
high  in  the  heavens,  shine  with  a  steady  light.  As  we 
always  see  it  through  the  more  or  less  misty  air  about  the 
horizon,  it  twinkles  and  sparkles  in  a  beautiful  manner. 
Hence  the  name  which  the  ancient  Greeks  so  poetically 
conferred  on  the  little  planet. 

As  Mercury,  owing  to  its  proximity  to  the  Sun,  is 
difficult  to  observe  with  the  unaided  eye,  it  is  also  diffi- 
cult to  observe  with  the  telescope.  The  opportunities 
of  favourable  observation  are  few,  so  closely  does  it  follow 
the  Sun.  The  first  thing  which  impresses  the  telescopic 
observer  of  Mercury  is  that  the  planet  exhibits  phases 
similar  to  those  of  the  Moon.  As  the  Earth's  path  en- 
closes the  orbits  of  both  Mercury  and  Venus,  we  never  see 
these  planets  fully  illuminated.  To  be  fully  illuminated 
a  body  must  be  in  the  opposite  quarter  of  the  heavens 
from  the  Sun,  like  the  Moon  at  the  full  phase.  Some- 
times, however,  Mercury  is  at  the  opposite  side  of  the 
Sun  from  our  planet.  That  is  to  say,  we  have  Mercury, 
the  Sun,  and  the  Earth  all  in  a  straight  line,  with  the 
Sun  between  the  Earth  and  Mercury.  The  planet  is 
then  at  its  farthest  from  the  Earth,  but  could  we  observe 
it  we  should  see  it  with  a  fully  illuminated  disc ;  in  fact, 
we  should  have  "full  Mercury."  We  do  not  see  the 
planet  at  these  "  superior  conjunctions  "  as  such  occurrences 
are  called,  for  Mercury  is  then  lost  in  the  glare  of  the 
Sun  and  quite  invisible  to  the  terrestrial  observer.  After 
a  time,  however,  the  planet,  in  its  journey  round  the  orb 

70 


MERCURY— "THE  SPARKLING   ONE" 

of  day,  reappears  from  the  solar  glare  as  an  evening  star. 
As  it  comes  nearer  and  nearer  to  the  Earth,  and  as  its 
disc  becomes  apparently  larger,  the  illuminated  portion 
decreases,  until  we  have  only  "half  Mercury,"  then  a 
crescent  Mercury,  until,  when  the  planet  is  at  its  nearest, 
the  thin  crescent  disappears  altogether  and  we  soon  have 
"new  Mercury."  Like  our  satellite  at  new  Moon,  Mer- 
cury becomes  invisible.  Technically  it  is  said  to  be  at 
"  inferior  conjunction,"  because  the  Earth,  Mercury,  and 
the  Sun  are  in  a  straight  line,  with  Mercury  in  the 
centre,  the  result  being  that  the  bright  side  of  the  planet 
is  turned  towards  the  Sun  and  away  from  the  Earth. 
Then  on  its  journey  round  the  Sun,  Mercury  again 
appears  as  "  morning  star."  Only  a  little  crescent  is 
at  first  visible  in  the  telescope,  but  gradually  the  illu- 
minated portion  becomes  greater  as  the  planet  recedes 
from  the  Earth  and  the  apparent  diameter  decreases. 
Again  we  have  "half  Mercury,"  and  again  the  planet 
disappears  in  the  rays  of  the  Sun  to  reappear  as  an 
evening  star. 

Thus  we  are  placed  at  a  disadvantage  in  regard  to  the 
observation  of  Mercury,  because  the  planet  revolves  round 
the  central  orb  within  the  orbit  of  the  Earth.  When 
Mercury  is  nearest  to  us  it  is  invisible.  When  it  is  fully 
illuminated  it  is  also  invisible.  We  only  see  it  bit  by 
bit,  as  it  were,  at  its  various  phases.  Above  all,  it  is 
so  near  the  Sun  that  astronomers  are  never  able  to 
observe  it  on  a  dark  background,  and  it  is  so  low  in 
the  heavens  that  it  is  always  seen  through  a  stratum 
of  thick  air. 

For  many  years  nothing  was  known  of  the  surface  of 
Mercury.  At  the  beginning  of  the  nineteenth  century, 
however,  a  series  of  observations  were  made  by  Schroter, 

71 


MERCURY— « THE   SPARKLING  ONE" 

an  able  German  astronomer  of  that  day.  Schroter  was 
anxious  to  ascertain  the  period  of  Mercury's  rotation  on 
its  axis — the  length  of  the  planet's  "day."  Schroter 
detected  certain  markings,  and  from  the  motions  of  those 
he  concluded  that  the  rotation  of  Mercury  was  performed 
in  about  twenty-four  hours,  similar  to  our  own  terres- 
trial day.  For  many  years  this  estimate  was  generally 
accepted,  although  owing  to  the  great  difficulty  of  observ- 
ing the  planet  it  was  not  implicitly  relied  on. 

Some  distinguished  astronomers,  however,  were  not 
content  with  a  mere  unconfirmed  estimate  of  the  length 
of  Mercury's  day.  Among  these  was  Schiaparelli  of 
Milan,  who,  in  1882,  commenced  a  prolonged  series  of 
observations  of  the  planet  for  the  purpose  of  determining 
the  rotation  period.  Previous  observers  had  been  handi- 
capped by  the  fact  that  Mercury  when  visible  as  an 
evening  or  morning  star  is  to  be  seen  for  only  a  short 
period.  Therefore  prolonged  observations  of  the  planet 
are  impossible  under  such  conditions.  Schiaparelli  struck 
out  a  new  line.  Instead  of  observing  Mercury  at  the 
usual  time,  he  followed  it  by  day,  considering  that  the 
disadvantage  of  observing  the  planet  in  the  day-time  was 
more  than  compensated  by  the  advantage  of  prolonged 
observation.  He  followed  the  planet  for  hours  at  a  time, 
and  at  last,  after  seven  years'  observations,  he  announced 
his  discoveries.  They  were  as  startling  as  they  were  un- 
expected. He  found  that  so  far  from  the  planet  rotating 
on  its  axis  in  twenty-four  hours,  the  markings  visible 
remained  fixed  in  position,  and  that  the  planet  performs 
only  one  rotation  on  its  axis  during  its  revolution  round 
the  Sun.  Instead  of  rotating  in  twenty-four  hours,  as 
the  Earth  does,  it  rotates  in  eighty-eight  of  our  terrestria  1 
days.  Controversy  raged  for  some  years  among  astro - 

72 


MERCURY— « THE  SPARKLING  ONE" 

nomers  as  to  the  accuracy  of  this  result,  but  now  the 
truth  of  Schiaparellfs  discovery  is  generally  accepted. 

Let  us  try  to  imagine  what  sort  of  a  world  Mercury 
must  be.  Rotating  on  its  axis  only  once  during  its 
journey  round  the  orb  of  day,  it  turns  the  same  face  to 
the  Sun  just  as  the  Moon  does  to  the  Earth.  One  face 


Superior 


Greatest 
Easlern         "i     Sun    P-        Western 


& 


Inferior 
Conjunction 

\ 


Earth 


FIG.  4.— Orbit  and  Phases  of  an  Inferior  Planet. 

of  the  planet  is  bathed  in  perpetual  sunshine,  the  other  is 
shrouded  in  everlasting  night.  One  side  is  baked  with 
heat,  and  the  other  is  frozen  with  cold.  No  wonder  that 
the  surface,  as  the  observations  of  Professor  Lowell  indi- 
cate, is  cracked  in  all  directions.  The  surface  of  Mercury, 
he  says,  is  colourless  :  "a  geography  in  black  and  white." 

73 


MERCURY— "THE  SPARKLING  ONE" 

However,  there  is  a  small  zone  on  the  planet's  surface  on 
which  the  Sun  does  rise  and  set — owing  to  the  irregular 
motion  of  the  planet  in  its  path,  its  varying  velocity 
due  to  the  eccentricity  of  its  orbit,  and  its  uniform 
motion  on  its  axis.  This  is  clearly  explained  by  Mr.  Gore 
in  the  following  words :  "  This  difference  in  the  regu- 
larity of  the  two  motions  will  of  course  give  rise  to  a 
6  libration,'  which  will  have  the  effect  of  bringing  a 
portion  of  the  dark  side  of  Mercury  periodically  into  the 
sunlight,  and  will  thus  diminish  the  area  of  the  planet's 
surface  which  is  shrouded  in  perpetual  night.  About 
three-eighths  of  the  total  surface  will  for  ever  remain  in 
darkness,  three-eighths  in  perpetual  sunshine,  while  the 
remaining  one-fourth  will  have  alternately  day  and  night. 
In  fact,  an  inhabitant  living  near  the  mean  bounding  line 
and  on  the  planet's  equator  would  have  forty-four  days 
of  sunshine  and  forty-four  days  of  night  and  twilight. 
A  little  farther  in  on  the  dark  side  there  would  be  per- 
petual twilight ;  and  farther  in  still,  eternal  night  would 
reign.  Owing  to  the  low  altitude  attained  by  the  Sun 
near  the  bounding  line,  its  intense  heat  and  light  would 
of  course  be  much  mitigated,  so  that  probably  this  region 
of  the  planet's  surface  may  be  comparable  with  the 
temperate  zones  of  the  Earth." 

Little  is  known  of  the  markings  of  Mercury.  The  few 
observations  which  astronomers  possess  seem  to  indicate 
that  the  surface  is  rugged  and  mountainous,  somewhat 
similar  to  that  of  the  Moon.  As  to  whether  there  is  an 
appreciable  atmospheric  envelope  surrounding  Mercury, 
opinion  is  divided,  some  holding  that  the  globe  of  Mercury 
is,  like  that  of  our  satellite,  airless,  others  believing  that 
there  is  an  atmosphere  surrounding  the  little  planet. 

The  general  opinion  of  astronomers  is  that  under  such 

74 


MERCURY— "THE   SPARKLING  ONE" 

conditions  as  exist  on  Mercury,  life,  as  we  know  it,  is  im- 
possible. If  there  are  inhabitants  of  Mercury,  they  must, 
from  the  dark  side  of  their  world,  obtain  magnificent 
views  of  the  outer  universe.  Venus  and  the  Earth  will 
shine  with  a  glorious  radiance,  fully  illuminated.  The 
Earth  and  Moon  seen  from  Mercury  form  a  fine  double 
star.  The  Earth  will  appear  a  magnificent  object, 
attended  by  a  little  star  of  the  third  magnitude.  The 
brightest  object  in  the  evening  skies  of  Mercury  will  be 
Venus,  as  the  little  planet  has  no  satellite  circling  round 
it  and  illuminating  its  dark  hemisphere. 


75 


CHAPTER   VII 
THE   EVENING   STAR 

FROM  the  earliest  ages  the  planet  Venus  has  been 
known  to,  and  admired  by,  mankind.  No  record  exists 
of  the  recognition  of  this  beautiful  planet  as  distinct 
from  the  ordinary  stars,  for  of  all  the  "  wanderers ""  Venus, 
as  the  brightest,  would  probably  be  the  first  to  be  detected. 
Homer  refers  to  the  star  as  the  "  star  of  Lucifer,"  and  one 
distinguished  astronomer  holds  that  under  the  title  of 
"  Mazzaroth  "  it  is  referred  to  in  the  Book  of  Job. 

Venus  is  both  the  evening  star  and  the  morning  star. 
That  is  to  say,  the  phenomena  known  as  evening  star  and 
morning  star  are  different  appearances  of  the  same  orb. 
The  earliest  astronomers  amongst  the  Greeks  did  not 
know  this.  The  morning  star  they  called  "  Phosphorus  " 
and  the  evening  star  "  Hesperus,"  and  for  many  years  the 
two  were  believed  to  be  separate  bodies.  It  was  noticed, 
however,  that  when  the  evening  star  was  to  be  seen  in  the 
evening,  there  was  no  trace  of  the  morning  star  on  the 
following  morning,  and  that  conversely  when  the  morning 
star  was  visible,  it  was  hopeless  to  expect  to  see  it  at 
night  at  the  same  period.  Pythagoras,  the  famous  Greek 
thinker,  is  believed  to  have  been  first  in  identifying  the 
two  stars  as  one — the  evening  and  morning  star. 

Venus,  like  Mercury,  exhibits  phases  when  observed  with 
the  telescope.  As  Venus  is  so  much  nearer  than  Mercury, 
and  is  a  much  larger  planet,  these  phases  are  much  more 

76 


THE  EVENING  STAR 

easily  observed.  To  the  unaided  eye  Venus  is  but  a 
luminous  point,  bright  enough  on  rare  occasions  to  cast 
shadows,  but  with  no  definite  shape.  When,  however,  we 
turn  even  a  small  telescope  on  the  evening  star,  a  remark- 
able change  is  wrought.  The  beautiful  soft  luminous 
point  is  transformed  into  an  exquisite  little  disc  of 
varying  phases,  for  Venus,  in  Galileo's  phrase,  "  imitates 
the  phases  of  the  Moon."  The  existence  of  these  phases 
was  affirmed  by  Copernicus  when  he  propounded  the 
theory  of  the  planetary  system.  The  existence  of  these 
phases  was  a  necessary  proof  of  his  contention  that  the 
planets  went  round  the  Sun,  and  not  round  the  Earth. 
It  was  pointed  out  to  Copernicus  that  no  phases  of  Venus 
could  be  seen,  and  in  those  days  there  were  no  telescopes. 
"  God,"  replied  Copernicus  to  his  critics,  "  will  cause 
instruments  to  be  invented  to  improve  the  sight  and  then 
you  will  see  them."  Soon  after  the  invention  of  the  tele- 
scope, in  1611,  Galileo  turned  his  instrument  on  the  even- 
ing star,  and  there,  in  the  field  of  the  telescope,  shone  an 
exquisitely  beautiful  miniature  of  the  Moon,  going  through 
each  of  our  satellite's  phases.  As  a  telescopic  object 
Venus  is  indeed  beautiful.  The  observation  of  the  planet 
is  a  source  of  never-ending  delight.  No  one  can  avoid 
feeling  a  thrill  of  pleasure  as  he  beholds  the  beautiful  even- 
ing star,  shining  out  softly  in  the  twilight,  with  its  calm 
and  rich  radiance,  transformed  by  the  telescope  into  an  ever 
changing  golden  disc,  sharply  defined  in  the  evening  light. 
The  phases  of  Venus  are  similar  to  those  of  Mercury. 
At  "  superior  conjunction  "  the  disc  of  the  planet  is  fully 
illuminated,  but  it  is  lost  in  the  rays  of  the  Sun.  Then 
the  planet  emerges  from  the  sunlight  as  "  evening  star." 
When  it  reaches  its  "  greatest  elongation  east,"  the  disc 
is  half  illuminated  like  the  Moon  at  the  quarters.  As 

77 


THE   EVENING   STAR 

the  planet  approaches  the  Earth  the  disc  increases  in 
size,  but  the  illuminated  portion  decreases  until  the 
planet,  a  dwindling  crescent,  is  again  lost  in  the  rays  of 
the  Sun  at  "inferior  conjunction,"  and  we  have  "new 
Venus."  The  planet  is  at  its  nearest  only  some  twenty- 
six  millions  of  miles  from  the  Earth,  but  it  is  invisible. 
Shortly  after  this  it  reappears  as  morning  star,  a  thin 
crescent  increasing  in  size,  and  its  apparent  diameter 
decreasing.  When  it  reaches  its  "greatest  elongation 
west,"  Venus  is  in  its  best  position  for  observation  as 
morning  star.  The  disc  becomes  smaller,  more  and  more 
of  it  becoming  visible,  until  it  draws  close  to  the  Sun, 
once  again  passes  superior  conjunction,  and  emerges  from 
the  sunset  as  evening  star. 

Our  knowledge  of  the  configuration  of  the  surface  of 
the  planet  is  very  limited,  for  two  reasons.  In  the  first 
place,  Venus  is,  like  Mercury,  unfortunately  placed  for 
observation.  It  is,  of  course,  easier  to  observe  than 
Mercury,  being  much  farther  from  the  Sun  and  much 
larger,  but,  like  that  orb,  it  is  never  seen  on  a  dark  sky, 
and  never  observed  for  a  protracted  period.  In  the 
second  place,  the  planet  is  so  dazzlingly  bright  that 
it  is  very  difficult  to  observe  markings  on  its  surface. 
Venus  reflects  a  greater  proportion  of  the  light  which 
it  receives  from  the  Sun  than  any  other  planet.  As  Mr. 
G.  F.  Chambers  remarks  in  his  book,  "  The  Story  of  the 
Solar  System,"  "  the  reflective  power  of  Venus  was  pro- 
bably never  more  effectively  brought  under  the  notice  of 
a  human  eye  than  on  September  6,  1878,  when  Nasmyth 
enjoyed  an  opportunity  of  seeing  Venus  and  Mercury  side 
by  side  for  several  hours  in  the  same  field  of  view.  He 
speaks  of  Venus  as  resembling  clear  silver,  and  Mercury 
as  nothing  better  than  lead  or  zinc.  Seeing  that  owing 

78 


THE   EVENING   STAR 

to  its  greater  proximity  to  the  Sun,  the  light  incident  on 
Mercury  must  be  three  and  a  half  times  as  strong  as  the 
light  incident  on  Venus,  it  follows  that  the  reflective 
power  of  Venus  must  be  very  great."  This  reflective 
power  has  been  estimated  as  equal  to  that  of  newly  fallen 
snow.  The  evening  star  reflects  seventy  per  cent,  of 
the  light  which  falls  on  it.  What  is  the  reason  of  this 
remarkable  reflective  power  ?  The  generally  accepted 
explanation  is  that  the  planet  is  surrounded  by  a  very 
dense  and  cloud-laden  atmosphere,  and  that  the  sunlight 
falls  on  these  clouds.  In  other  words,  we  rarely  catch  a 
glimpse  of  the  surface  of  Venus.  This  is  fully  confirmed 
by  observation  of  the  planet.  It  is  only  with  the  greatest 
difficulty  that  the  markings  can  be  detected. 

As  in  the  case  of  Mercury,  the  length  of  the  planet's 
day  has  been  for  many  years  a  matter  of  controversy. 
Observations  made  in  the  seventeenth  century  by  the 
famous  astronomer,  Cassini,  indicated  that  Venus  turned 
on  its  axis  in  a  period  of  about  twenty-three  hours.  At 
the  same  time,  however,  another  astronomer,  Bianchini, 
made  observations  which  suggested  a  period  of  twenty- 
four  days,  eight  hours.  The  German  astronomer  Schroter, 
tackled  the -question  at  the  end  of  the  eighteenth  century, 
and  confirmed  the  short  period  of  twenty-three  hours. 
In  1839  an  Italian  astronomer,  Di  Vico,  confirmed 
these  observations,  and  for  fifty  years  the  twenty-three 
hour  period  was  generally  accepted.  It  was  the  same 
distinguished  astronomer  who  showed  the  probability  of 
the  long  rotation  period  of  Mercury  who  made  the  same 
discovery  in  regard  to  Venus. 

A  series  of  observations,  extending  over  thirteen  years, 
convinced  Schiaparelli  that  the  markings  noted  by  the 
earlier  observers  were  not  really  permanent.  As  in  the 

79   ' 


THE  EVENING   STAR 

case  of  Mercury,  he  observed  the  planet  by  day,  and  was 
enabled  to  follow  it  for  hours  at  a  time.  He  concentrated 
his  attention  on  round  white  spots  which  remained  fixed 
in  position.  The  obvious  conclusion  to  be  drawn  from 
this  is  that  Venus  performs  only  one  rotation  on  its  axis 
in  its  period  of  revolution  round  the  Sun — 225  days.  One 
face  of  the  planet  is  constantly  turned  to  the  Sun,  and  in 
continuous  sunlight ;  the  other  face  is  always  turned  from 
the  Sun,  and  is  in  everlasting  darkness.  In  the  case  of 
Venus  there  is  not  the  same  amount  of  "  libration "  as 
in  that  of  Mercury.  The  pathway  of  Venus  is  much 
more  nearly  circular,  and  the  variation  of  velocity  is  much 
less  than  in  the  case  of  the  smaller  planet,  so  that  only  a 
very  small  part  of  the  surface  will  enjoy  the  alternation  of 
night  and  day  as  does  a  considerable  portion  of  Mercury. 

Since  Schiaparelli  announced  his  results,  a  number  of 
different  observers  have  made  observations  to  determine 
the  rotation  period.  The  period  of  225  days  has  been 
abundantly  confirmed  by  observers  favoured  by  good  cli- 
mates and  clear  skies,  while  astronomers  in  less  favourable 
climates  supported  the  short  period.  It  may  be  now  taken 
as  veiy  probable  therefore  that  Venus  rotates  on  its  axis 
in  the  same  period  as  it  requires  to  revolve  round  the  Sun 

Little  is  known  of  the  physical  condition  of  the  planet 
owing  to  the  dense  atmosphere  which  surrounds  it.  Polar 
"caps,"  supposed  by  some  to  be  somewhat  similar  to 
those  on  our  own  planet  and  on  Mars,  have  been  observed, 
or  at  least  "  suspected,"  from  time  to  time.  Some  astro- 
nomers, however,  do  not  regard  them  as  snow ;  the  drawings 
of  Schiaparelli  represent  them  as  separated  by  a  dark 
shadow,  which  suggests  that  they  represent  two  mighty 
mountain  systems.  Evidence  of  the  mountainous  con- 
dition of  Venus  was  obtained  by  Schroter  as  long  ago  as 

80 


THE  EVENING   STAR 

the  beginning  of  last  century.  He  noted  the  southern 
"horn"  of  the  planet  when  in  the  crescent  form  to  be 
blunted,  and  he  attributed  this  to  the  existence  of  a  great 
mountain,  five  or  six  times  higher  than  the  loftiest  peaks 
on  the  Earth.  Along  the  terminator,  or  the  dividing 
line  between  light  and  darkness,  he  noted  irregularities 
which  he  considered  to  be  more  strongly  marked  than 
those  on  the  Moon.  These  observations  have  since  been 
only  partly  confirmed.  Still  there  seems  fairly  strong 
evidence  that  the  surface  is  rocky  and  mountainous, 
although  not  so  mountainous  as  was  believed  by  Schroter. 
Trouvelot,  a  French  astronomer,  found  in  1878  the  polar 
spots  distinctly  visible.  "  Their  surface,"  he  wrote,  "  is 
irregular,  and  seems  like  a  confused  mass  of  luminous 
points,  separated  by  comparatively  sombre  intervening 
spaces.  This  surface  is  undoubtedly  very  broken,  and  re- 
sembles that  of  a  mountainous  district  studded  with  numer- 
ous peaks,  or  our  polar  regions  with  numerous  ice-needles 
brilliantly  reflecting  the  sunshine."  These  features,  then,  are 
either  striking  enough  to  be  seen  through  the  dense  cloud- 
canopy  which  surrounds  Venus,  or  else  they  are  high  enough 
to  project  above  the  dense  portions  of  the  atmosphere. 

Of  the  existence  of  the  atmosphere  there  is  no  doubt. 
It  has  been  actually  observed  when  the  planet  is  in 
"  transit  "  across  the  face  of  the  Sun.  Spectroscopic  ob- 
servations show  that  water  vapour  exists  in  the  atmosphere, 
which  is  very  dense.  Seen  from  the  Earth,  this  atmosphere 
seems  the  very  picture  of  calm  and  quiescence.  But  if  the 
long  period  of  rotation  indicated  by  Schiaparelli's  obser- 
vations be  correct,  it  can  scarcely  be  a  calm  region.  As 
a  recent  writer  puts  it :  "  The  atmosphere  circulation  of 
Venus  must  be  conducted  by  a  permanent  hurricane  system. 
A  violent  uprush  of  heated  air  on  the  side  perpetually 

81  F 


THE  EVENING  STAR 

exposed  to  a  glare  twice  as  fierce  as  that  of  our  hottest 
sun,  should  be  compensated  for  by  a  furious  inrush  on 
both  sides  of  the  illuminated  hemisphere,  like  the  draught 
caused  by  a  fire  in  a  cold  room."" 

Venus  has  no  satellite,  in  this  respect  resembling  Mercury. 
For  many  years,  nevertheless,  a  search  for  a  satellite  was 
prosecuted  with  great  energy,  and  it  was  believed  by 
several  astronomers  that  they  had  detected  a  companion- 
world.  It  was  afterwards  shown,  however,  that  what  they 
had  taken  for  satellites  must  have  been  either  optical  illu- 
sions, caused  by  the  glare  of  the  planet  in  the  field  of  the 
telescope,  or  small  stars  which  happened  to  lie  in  the  same 
field  of  view  as  the  planet.  Thus,  although  in  size  resem- 
bling the  Earth  more  than  any  other  world,  it  differs  from 
our  planet  in  several  important  respects  ;  its  "  days  "  are 
utterly  different  from  ours,  and  it  has  no  Moon  to  circle 
round  it  and  perform  the  useful  offices  of  satellite-world. 

The  question  of  the  habitability  of  Venus  has  attracted 
little  attention.  Certainly  the  planet,  with  its  remarkable 
rotation  period,  and  its  dense  atmosphere,  does  not  seem 
an  inviting  abode.  On  this  point,  however,  astronomers 
know  too  little  to  speak  with  confidence.  Sir  Robert  Ball 
inclines  to  the  view  that  even  though  Venus  does  rotate 
in  the  way  that  the  majority  of  astronomers  believe,  "  we 
might  expect  to  find  in  that  planet  a  luxuriant  tropical 
life  of  a  kind  perhaps  analogous  to  life  on  the  Earth." 
If  there  are  inhabitants  of  Venus,  and  if  ever  they  catch 
a  glimpse  of  the  outer  universe,  their  eyes  will  be  gladdened 
by  a  beautiful  celestial  spectacle  such  as  we  on  this  planet 
are  not  privileged  to  see.  The  Earth  and  Moon,  com- 
bined, probably  appear  more  brilliant  to  Venus  than  Venus 
does  to  us,  and  the  two  orbs — the  smaller  moving  round 
the  larger — form  a  beautiful  and  imposing  double  star. 

82 


CHAPTER   VIII 
MARS— THE   RED   PLANET 

A  was  shown  in  the  previous  chapters,  Venus  revolves 
round  the  Sun  in  an  orbit  wholly  within  that  of 
the  Earth,  and  consequently  is  not  seen  by  us  to 
full  advantage.  When  nearest,  the  planet  is  invisible  ;  it 
is  in  a  straight  line  between  the  Earth  and  the  Sun,  and 
turns  its  dark  hemisphere  to  our  planet.  With  Mars 
the  case  is  entirely  different.  Mars  revolves  in  an  orbit 
exterior  to  ours,  and  when  nearest  to  the  Earth  is  on  the 
other  side  of  our  planet  from  the  Sun.  The  Sun,  the 
Earth,  and  Mars  are  in  a  straight  line  with  the  Earth  in 
the  middle.  If  the  near  approaches  of  Venus  correspond 
to  "New  Moon,"  those  of  Mars  correspond  to  "Full 
Moon."  We  then  see  Mars  with  a  full  round  disc.  The 
planet  is  said  to  be  "  in  opposition  "  to  the  Sun,  because 
it  is  in  the  .opposite  quarter  of  the  heavens.  It  rises  at 
sunset,  culminates  at  midnight,  and  sets  at  sunrise. 

Mars  as  a  celestial  spectacle  is  usually  inferior  to  Venus. 
But  at  times  its  brilliancy  becomes  extraordinary,  and  the 
planet  shines  with  a  bright  ruddy  light  which  makes  it 
one  of  the  most  striking  objects  in  the  heavens.  In  the 
words  of  a  famous  modern  astronomer :  "  Once  in  every 
fifteen  years  a  startling  visitant  makes  his  appearance  upon 
our  midnight  skies — a  great  red  star  that  rises  at  sunset 
through  the  haze  above  the  eastern  horizon,  and  then, 
mounting  higher  with  the  deepening  night,  blazes  forth 

83 


MARS— THE   RED   PLANET 

against  the  dark  background  of  space  with  a  splendour 
that  outshines  Sirius  and  rivals  the  giant  Jupiter  himself. 
Startling  for  its  size,  the  stranger  looks  the  more  fateful 
for  being  a  fiery  red.  Small  wonder  that  by  many  folk 
it  is  taken  fora  portent.'''  It  is  recorded  that  in  1719 
Mars  was  so  brilliant  that  a  panic  ensued  among  the 
ignorant.  Owing  to  the  comparative  nearness  of  Mars  to 
our  world — at  times  about  thirty-five  millions  of  miles 
— along  with  its  favourable  presentation  when  closest  to 
the  Earth,  we  know  more  of  the  surface  of  Mars  than  of 
any  other  body  in  the  entire  Universe,  with  the  single 
exception  of  the  Moon.  For  over  250  years  Mars 
has  been  attentively  studied  by  astronomers.  It  was 
observed  by  Galileo,  who,  however,  discovered  nothing 
important.  In  1656  the  Dutch  astronomer,  Huyghens, 
made  the  first  determination  of  the  length  of  the  Martian 
day,  the  period  of  the  planet's  rotation  on  its  axis.  Un- 
like Mercury,  Mars  has  a  day  somewhat  similar  to  our 
own,  the  length  of  which  has  been  known  for  over  two 
centuries.  The  exact  length,  to  within  a  fraction  of  a 
second,  is  24  hours  37  minutes  22 '65  seconds,  only  about 
half-an-hour  longer  than  the  day  of  our  own  world.  Its 
year,  therefore,  which  consists  of  687  of  our  days,  contains 
669  of  its  own.  In  another  particular  Mars  closely  re- 
sembles the  Earth.  The  inclination  of  its  axis  to  the  plane 
of  its  orbit  is  about  66  degrees ;  its  seasons,  therefore, 
closely  resemble  those  on  the  Earth.  Another  remarkable 
point  of  resemblance  was  noted  almost  two  centuries  ago. 
In  1719  the  French  astronomer  Maraldi  discovered  two 
white  spots  on  the  disc  of  Mars — one  at  the  north  pole, 
the  other  at  the  south.  These  spots  correspond  to  the 
polar  regions  of  our  own  planet. 

Like  the  Earth,  Mars  has  an  atmosphere,  but  it  is 

84 


THE  PLANET  MARS 

The  two  uppermost  drawings  are  by  Professor  Lowell,  July  8  and  12, 
1907.  The  lower  drawing  is  by  Professor  Schiaparelli,  May,  1890.  On  each 
the  polar  caps  and  the  famous  canals  are  visible. 


MARS— THE  RED  PLANET 

much  thinner  than  our  own,  "  thinner  at  least  by  half," 
says  Professor  Lowell,  "than  the  air  on  the  summit  of 
the  Himalayas."  Clouds  and  obscurations  seem  to  be 
very  rare  in  the  Martian  atmosphere.  It  is  very  clear 
and  transparent,  and  it  is  believed  not  to  differ  much 
from  our  own  in  constitution.  The  following  description 
of  this  Martian  atmosphere  is  from  the  pen  of  the  late 
Miss  Agnes  Clerke  :  "  This  slender  envelope  is  exceedingly 
extensive.  In  the  pure  sky,  scarcely  veiled  by  it,  the  Sun 
diminished  to  less  than  half  its  size  at  our  horizons,  pro- 
bably exhibits  its  coronal  streamers  as  a  regular  part  of 
his  noontide  glory ;  atmospheric  circulation  proceeds  so 
tranquilly  as  not  to  trouble  the  repose  of  a  land  *  in  which 
it  seemeth  always  afternoon.' r 

Huyghens  and  other  early  astronomers  detected  various 
prominent  markings,  chief  among  them  the  well-known 
features  known  variously  as  the  Kaiser  Sea,  the  Hour-Glass 
Sea,  and,  in  the  now  prevalent  system  of  nomenclature, 
the  Syrtis  Major.  It  was  not,  however,  until  Herschel  took 
up  the  study  of  Mars  that  much  was  known  of  its  surface. 
He  found  that  the  spots  at  the  poles  waxed  and  waned 
in  accordance  with  the  Martian  seasons — that  is  to  say, 
the  north  polar  cap  increased  in  size  during  the  winter 
of  the  northern  hemisphere,  and  decreased  in  summer, 
while  the  reverse  process  took  place  in  the  southern  hemi- 
sphere. He  concluded,  therefore,  that  the  polar  spots 
were  masses  of  snow  and  ice,  similar  to  the  polar  regions 
of  the  Earth.  After  the  planet  had  been  attentively 
studied  by  Beer  and  Miidler,  Dawes,  Secchi,  and  other 
astronomers,  the  late  Mr.  Proctor  constructed  a  map  of 
Mars  in  1869  from  drawings  by  Dawes.  He  gave  names 
to  the  various  features,  the  red  portions  of  the  planet's 
disc  being  known  as  continents,  and  the  green  as  seas,  in 

85 


MARS— THE   RED   PLANET 

accordance  with  the  prevailing  views  of  contemporary 
astronomers.  Along  with  this  he  put  forward  in  "  Other 
Worlds  than  Ours,"  some  very  fascinating  and  plausible 
ideas  of  the  habitability  of  Mars,  which  he  named  a 
"miniature  of  the  Earth,"  having  continents,  oceans, 
snow,  rain,  clouds,  rivers,  and  probably  inhabitants.  The 
researches  of  the  last  twenty-eight  years,  however,  have 
revolutionised  our  knowledge  of  Mars.  The  close  analogy 
which  Proctor  perceived  has  vanished,  and  Mars  is  now 
considered  as  an  emblem  of  what  our  world  will  be  in  the 
future  rather  than  as  a  miniature  at  present.  The  most 
recent  observations  have  changed  but  not  destroyed  the 
analogy. 

It  was  in  1877  that  the  revolution  in  our  views  con- 
cerning Mars  began.  In  the  words  of  Mr.  Percival  Lowell : 
"  Our  knowledge  of  the  planets,  and  especially  of  Mars, 
has  advanced  greatly  within  the  last  quarter  of  a 
century.  The  first  steps  of  this  advance  we  owe  not 
to  instruments,  but  to  the  genius  of  one  man — the 
Italian  astronomer  Schiaparelli."  1  When  in  September 
1877  the  planet  reached  its  opposition,  this  famous 
astronomer  commenced  a  trigonometrical  survey  of  the 
planet's  disc.  While  so  employed  he  discovered  a  number 
of  fine  dark  lines  crossing  the  red  areas  of  the  planet.  He 
called  them  "canali,"  an  Italian  word  meaning  canals 
or  channels.  In  1879  Professor  Schiaparelli  again 
observed  the  canals,  which  revealed  the  same  appear- 
ance as  they  had  done  two  years  previously.  Towards 
the  end  of  the  year  he  was  amazed  to  find  that  one  of  the 
canals  had  become  double — a  new  canal  running  parallel 
with  the  original  one.  Suspecting  optical  illusions  he 

1  It  is  claimed  that  some  of  the  more  prominent  canals  had  been 
noted  by  Mr.  Maunder  and  other  English  observers  before  1877. 

86 


MARS— THE  RED  PLANET 

changed  his  telescopes  and  eye-pieces,  but  was  soon  con- 
vinced of  the  reality  of  his  observations.  In  1881  he 
again  saw  the  canals,  double  and  single ;  and  during  the 
unfavourable  oppositions  of  1884,  1886,  and  1888,  he 
went  from  discovery  to  discovery.  Indeed,  he  declared 
in  1888  that  the  canals  had  all  the  distinctness  of  an 
engraving  on  steel  with  the  magical  beauty  of  a  coloured 
painting.  Considerable  scepticism  prevailed  in  scientific 
circles  for  a  number  of  years,  as  other  astronomers  could 
not  see  the  canals,  either  double  or  single.  At  length, 
in  1 886,  nine  years  after  the  Italian  astronomer  made  his 
discovery,  the  news  flashed  over  the  scientific  world  that 
his  discovery  was  confirmed.  In  that  year  the  astronomers 
at  the  Nice  Observatory  detected  the  canals.  They  were 
soon  followed  by  a  number  of  the  most  distinguished 
observers,  both  of  Europe  and  America,  who  testified  that 
the  canals  were  there,  however  much  astronomers  might 
differ  in  their  interpretation  of  them. 

In  1892  Professor  Pickering,  observing  in  the  fine 
climate  of  Arequipa,  on  the  slope  of  the  Andes  in  Peru, 
discovered  at  the  junctions  of  the  canals  dark  spots  which 
he  termed  "  lakes,"  in  keeping  with  the  view  that  the 
darker  regions  of  the  planet's  surface  are  really  aqueous ; 
but  his  observations  at  the  same  opposition  threw  con- 
siderable doubt  on  this  view.  For  the  purpose  of  ob- 
serving the  planet  thoroughly  during  the  favourable 
opposition  of  1894,  Mr.  Percival  Lowell  erected  a  special 
observatory  at  Flagstaff,  Arizona.  Observations  were 
there  commenced  on  May  29,  1894,  by  Mr.  Lowell  and 
his  assistant,  Mr.  Douglass,  and  were  continued  until 
April  3, 1 895,  when  the  favourable  season  for  observation 
came  to  an  end.  Altogether,  Mr.  Lowell  mapped  out 
three  hundred  and  fifty  canals,  and  obtained  confirmatory 

87 


MARS— THE   RED  PLANET 

evidence  of  the  existence  of  lakes  discovered  by  Professor 
Pickering.  Instead  of  lakes,  Mr.  Lowell  prefers  to  call 
them  "oases.11 

At  the  same  time  Professor  Lowell  made  what  he  calls 
a  Martian  polar  expedition.  On  3rd  June  1894  he 
measured  the  south  polar  cap  when  it  stretched  "  almost 
one  unbroken  waste  of  white,"  over  about  55  degrees  of 
latitude,  its  diameter  across  measuring  2035  miles.  As  it 
melted  there  was  observed  surrounding  it  a  broad  blue 
belt,  and  as  the  cap  contracted  the  belt,  which  evidently 
represented  the  water  let  loose  by  the  melting  of  the 
cap,  also  decreased  in  size.  In  August  1894  it  was,  in 
Professor  Lowell's  words,  "a  barely  discernible  thread 
drawn  round  the  tiny  white  patch,  which  was  all  that 
remained  of  the  enormous  snow  fields  of  some  months 
before."  On  12th  October  Mr.  Lowell  noted  in  his 
diary  :  "  Polar  cap  has  been  very  faint  for  some  time  ; 
barely  visible."  On  the  following  day  his  assistant,  on 
turning  the  telescope  on  Mars,  was  amazed  to  find  that 
the  cap  had  vanished.  This  was  the  first  occasion  on 
which  the  snow  cap  was  seen  to  disappear ;  and  this 
shrinkage  or  disappearance  of  the  cap  apparently  holds 
the  key  to  the  various  problems  of  the  Martian  disc. 

By  this  time  several  theories  had  been  put  forward 
to  account  for  the  phenomena  of  the  planet's  surface. 
Proctor  had  thrown  out  the  hint  that  the  canals  were 
rivers,  but  this  idea  was  soon  thrown  aside.  Various  other 
astronomers  regarded  the  canals  as  cracks  in  the  planet's 
surface,  as  swarms  of  meteors  ploughing  tracks  above  the 
planet,  and  as  chains  of  mountains  running  over  land  and 
sea  ;  but  each  of  these  hypotheses  was  in  turn  abandoned  as 
untenable.  In  the  end  of  1895  Mr.  Lowell's  views  on  the 
planet — the  result  of  his  own  observations — were  given  to 

88 


MARS— THE   RED   PLANET 

the  world  in  his  book,  "  Mars."  Mr.  Lowell  concludes  that 
the  reddish  ochre  portions  of  the  planet — the  "  continents  " 
of  Proctor — are  desert  land  ;  that  the  dark  regions  are  not 
seas,  but  marshy  tracts  of  vegetation,  and  that  the  polar 
caps  are  composed  of  snow  and  ice.  He  adopts  Professor 
Schiaparelli's  view  that  the  canals  are  waterways,  lined  on 
either  side  by  banks  of  vegetation,  as  well  as  Professor 
W.  H.  Pickering's  idea  that  the  lines  which  we  see  are 
not  the  canals  themselves — which  are  much  too  small  to  be 
seen — but  the  strip  of  fertilised  ground  surrounding  them. 
The  canals  are  distinctly  connected  with  the  melting  of 
the  polar  cap,  and  grow  darker  as  the  cap  melts,  just  as  if 
water  was  being  conveyed  along  them.  All  this  is  very 
easily  explained  by  one  assumption — namely,  that  the 
canals  have  been  constructed  by  a  race  of  intelligent 
beings  for  the  specific  purpose  of  bringing  water  from  the 
melting  polar  cap  to  the  equator.  Mars  is  scarce  of 
water ;  and  if  there  are  inhabitants  they  must  be  com- 
pelled to  utilise  every  drop  which  they  can  secure.  The 
oases  are  supposed  by  Mr.  Lowell  to  represent  centres  of 
population  where  the  inhabitants,  driven  from  the  desert 
land  by  scarcity  of  water,  cluster  about  the  ground 
artificially  fertilised.  Mr.  Lowell  also  concludes  that  as 
Mars  is  an  older  planet  than  the  Earth,  the  inhabitants 
are  probably  in  a  higher  state  of  civilisation.  Thus,  all 
the  complicated  Martian  phenomena  are  explained  on 
the  assumption  that  Mars  is  inhabited  by  a  race  of 
intelligent  beings. 

This  theory  was  not  cordially  received,  and  astronomers 
began  to  consider  if  some  other  explanation  would  not  be 
more  probable.  Most  scientists  inclined  to  what  is 
known  as  the  "optical  illusion  theory,"  put  forward 
originally  by  the  eminent  Italian  astronomer,  Signor 

89 


MARS— THE  RED  PLANET 

Vincenzo  Cerulli  of  Teramo,  and  independently  by  Mr. 
E.  W.  Maunder,  of  Greenwich  Observatory,  the  well- 
known  English  astronomer.  It  was  supported  by  Professor 
Simon  Newcomb,  who  thus  explains  the  "  canaliform " 
appearance  :  "  This  phenomenon  is  not  to  be  regarded  as  a 
pure  illusion  on  the  one  hand,  or  an  exact  representation 
of  objects  on  the  other.  It  grows  out  of  the  spontaneous 
action  of  the  eye  in  shaping  slight  and  irregular  combina- 
tions of  light  and  shade  too  minute  to  be  separately  made 
out,  into  regular  forms.11  A  series  of  experiments  made 
by  Mr.  Maunder  in  1902  and  1903  were  described  by 
him  in  Knowledge  for  November  1903.  In  conjunction 
with  Mr.  Evans,  headmaster  of  the  Royal  Hospital  School 
of  Greenwich,  Mr.  Maunder  arranged  for  classes  of  two 
hundred  boys  to  copy  at  different  distances  three  views 
of  Mars  on  which  the  canal  system  was  not  represented. 
As  almost  all  the  boys  drew  canals  on  the  copies,  Mr. 
Maunder  considers  that  the  optical  illusion  theory  is 
finally  proved.  But  Mr.  Lowell  answers  him  by  the 
following  criticism  of  the  theory  : — "  It  asserts  that 
because  of  the  tendency  of  the  human  eye  to  connect 
well-seen  points  by  imaginary  lines,  therefore  those  on 
Mars  are  of  this  class  ;  which  is  like  saying  that  because  a 
man  may  see  stars  without  looking  at  the  heavens,  there- 
fore those  in  the  sky  do  not  exist.  The  parallel  is  not 
simply  for  illustration ;  it  is  exact,  for  the  nervous  action 
of  the  optic  lobes  will  similarly  cause  any  one  to  see  faint 
points  of  light  in  a  darkened  field  of  vision,  and  the  whole 
art  of  the  observer  consists  in  distinguishing  which  of  these 
phenomena  are  objective  and  which  not.  So  with  these  lines. 
A  little  more  experience  than  the  boys  possessed  would 
have  permitted  of  parting  the  true  lines  from  the  false/1 
Mr.  Lowell's  observations  on  Mars,  at  the  opposition 

90 


MARS— THE  RED  PLANET 

of  1903,  were  distinctly  confirmatory  of  this  theory.  He 
made  use  of  his  various  drawings  "to  determine  the 
degree  of  visibility  of  a  given  canal  at  different  seasons 
of  the  Martian  year."  After  eliminating  all  sources  of 
error,  Mr.  Lowell  was  able  to  construct  graphs  or  curves 
of  the  visibility  of  the  canals,  and  thus  formed  a  series 
of  curves  which  he  named  cartouches.  From  a  dis- 
cussion of  these  cartouches,  Mr.  Lowell  finds  that  the 
development  of  the  canals  does  not  commence  until  the 
polar  cap  begins  to  melt ;  but  after  the  cap  melts  the 
canals  develop  down  the  latitudes  past  the  equator  into 
the  opposite  hemisphere.  He  finds  that  it  takes  the 
water  fifty  days  to  travel  from  latitude  72°  N.  to  the 
equator,  a  distance  of  2650  miles.  "  This  means  a  speed 
of  fifty-one  miles  a  day,  or  2'1  miles  an  hour,  and  here 
we  confront  the  surprising  part  of  the  performance,  for 
the  transference  takes  place  in  the  face  of  gravity.  A 
particle  of  water  or  other  liquid  would  know  no  inclina- 
tion to  move  from  where  it  found  itself.  Gravity 
would  not  solicit  it  to  stir.  Of  its  own  accord  it  would 
not  move  from  the  pole  to  the  equator.  Now,  as  it 
does  flow  towards  the  equator,  and  with  a  remarkably 
steady  progression  too,  the  inference  seems  inevitable 
that  it  has  been  carried  thither  by  artificial  means. " 
In  1905  and  1907  Mr.  Lowell  succeeded  in  photograph- 
ing the  canals.  His  first  photographs  secured  a  number 
of  converts,  if  not  to  his  opinion,  at  least  to  belief  in 
these  remarkable  objects. 

Mr.  Lowell  hailed  his  success  in  1905  as  the  refutation 
of  the  opposing  theory.  As  the  photographic  plate 
cannot  be  the  victim  of  illusion  the  canals  should,  on 
the  illusion  theory,  be  represented  by  irregular  dots 
instead  of  straight  dark  lines.  As  Mr.  Lowell  remarked 

91 


MARS— THE  RED  PLANET 

in  a  communication  to  the  present  writer,  "  the  camera 
does  not  agree  with  the  arm-chair  critics  of  the  canals, 
but  will  have  it  that  these  markings  are  lines."  Never- 
theless the  supporters  of  the  illusion  theory  still  hold 
to  a  modified  form  of  it.  In  their  latest  work,  published 
in  the  end  of  1908,  Mr.  and  Mrs.  Maunder  have  the  fol- 
lowing remarks  :  "  Are  these  markings  on  Mars  actually 
as  we  see  them,  or  do  we  only  see  them  like  that  ?  We 
have  no  right  to  conclude  that  the  straight  sharp  even 
'  canals '  we  see  on  the  surface  of  Mars  are  really  as 
artificial  as  they  seem  to  us." 

Some  remarkable  observations  of  the  canals  were  made 
by  Professor  Lowell  at  the  "  opposition  "  of  the  planet  in 
1909.  On  September  30  of  that  year,  when  the  region 
known  as  the  Syrtis  Major  was  presented  to  view,  two 
very  prominent  canals  became  evident.  "Not  only," 
says  Professor  Lowell,  "was  their  appearance  unpre- 
cedented, but  the  canals  themselves  were  the  most  con- 
spicuous ones  on  this  part  of  the  disc.  Many  drawings 
were  made,  and  in  the  course  of  the  next  few  days  the 
new  canals  were  photographed,  appearing  on  the  plates 
as  the  most  salient  canals  in  their  part  of  the  planet. 
The  record  books  were  then  examined,  when  it  appeared 
that  not  a  trace  of  them  was  to  be  found  in  the  drawings 
of  August,  July,  June,  or  May,  when  this  part  of  the 
planet  was  depicted.  That  they  had  not  been  observed 
in  previous  years  was  then  conclusively  ascertained  by 
examination  of  the  records  of  those  years." 

Professor  Lowell  shows  that  these  canals  were  never 
seen  before,  either  by  himself  or  by  Schiaparelli,  or  by 
any  other  observer.  "It  might  seem,"  he  says,  "that 
the  absence  on  the  charts  was  proof  that  a  canal 
was  itself  new  in  the  second  sense,  because  it  was  so  in 


MARS— THE   RED   PLANET 

the  first.  But  study  of  Mars  has  shown  that  this  cannot 
be  taken  off-hand  for  granted ;  several  points  must  each 
be  carefully  considered.  In  the  first  place,  one  must  be 
sure  that  the  phenomenon  could  have  been  seen  before, 
yet  was  not.  It  must  be  of  a  size  which  could  not  have 
escaped  detection  previously.  In  the  present  case,  how- 
ever, this  possibility  of  error  was  excluded  by  the  size 
of  the  canals  in  question." 

Mr.  Lowell  in  his  announcement  of  the  discovery 
merely  says  that  the  proofs  are  clear  that  two  new  canals 
have  developed.  The  inference  in  harmony  with  the 
theory  which  he  maintains,  that  the  canals  are  artificial, 
is  that  two  new  waterways  have  been  constructed  by 
intelligent  beings.  A  good  deal  of  scepticism  has  been 
aroused  by  a  theory  so  startling,  and  few  astronomers 
seem  inclined  to  follow  the  American  astronomer  in  the 
latest  development  of  his  theory.  Still,  if  the  theory  in 
its  general  outline  be  correct,  there  is  nothing  either 
impossible  or  fantastic  in  Professor  Lowell's  explanation 
of  the  remarkable  change  which  he  has  observed  on  the 
surface  of  Mars.  Considerable  space  has  been  given  here 
to  the  various  theories  of  the  canals,  because  these  re- 
markable objects  have  not  only  attracted  widespread 
attention,  but  have  for  years  constituted  a  different 
astronomical  problem. 

As  was  pointed  out  at  the  beginning  of  this  chapter, 
more  is  known  of  the  surface  of  Mars  than  of  any  other 
body  except  the  Moon.  Our  knowledge  of  the  planet's 
geography,  or  rather  "  aerography,"  is  well-nigh  complete. 
As  Professor  Lowell  says :  "  Aerography  is  a  true  geo- 
graphy, as  real  as  our  own.  Quite  unlike  the  markings 
on  Jupiter  and  Saturn,  where  all  we  see  is  cloud,  in 
the  markings  on  Mars  we  gaze  upon  the  actual  surface 

93 


MARS— THE  RED  PLANET 

features  of  the  Martian  globe.  They  change  in  appear- 
ance, indeed,  according  to  times  and  seasons,  but  they 
alter  as  true  surface  features  would,  not  like  cloud  belts  that 
gather  to-day  and  vanish  to-morrow."  For  these  mark- 
ings a  number  of  different  systems  of  names  have  been  in 
vogue.  Proctor  was  the  first  to  draw  up  a  real  geography 
of  the  planet.  He  named  the  features  after  well-known 
astronomers,  such  as  Herschel  Continent,  Miidler  Continent, 
Dawes  Ocean,  Kaiser  Sea.  Flammarion  drew  up  another 
chart,  with  a  different  set  of  names.  For  instance,  the 
Kaiser  Sea  became  in  Flammarion's  system,  "Mer  du 
Sablier."  Green,  another  English  astronomer,  invented 
another  system.  Finally  Schiaparelli  re-named  all  the 
features  on  the  disc,  and  in  this  nomenclature  he  is  followed 
by  Lowell  and  most  modern  students  of  Mars.  His  names 
are  drawn  from  classical  mythology,  and,  being  Latin,  have 
the  advantage  of  commending  themselves  to  astronomers 
of  all  nations.  In  this  system  the  Kaiser  Sea — the  best 
known  object  on  the  red  planet — becomes  the  Syrtis 
Major.  The  canals  are  named  after  mythological  and  real 
terrestrial  rivers.  Thus  we  find  on  Mars  the  Euphrates 
and  the  Ganges.  This  system  devised  by  Schiaparelli  is 
now  in  general  use. 

The  canals  vary  greatly  in  length  and  in  width.  Many 
of  them  are  about  2000  miles  long.  One  known  as  the 
Eumenides-Orcus  is  3540  miles,  altogether  an  enormous 
length  on  a  globe  as  small  as  Mars.  The  larger 
canals  are  estimated  as  from  fifteen  to  twenty  miles  in 
width,  and  the  smaller  from  two  to  three  miles.  As  to 
their  number,  several  hundreds  have  been  catalogued 
by  Schiaparelli  and  Lowell,  and  as  the  last-named  astro- 
nomer says,  "  their  name  collectively  is  legion ;  while  to 
name  them  individually  is  fast  getting,  for  the  number 

94 


MARS— THE   RED  PLANET 

detected,  to  be  impossible."  The  geography  of  Mars  is 
truly  a  marvellous  one,  so  much  does  it  resemble,  and  at  the 
same  time  so  much  does  it  differ  from  our  own.  Whatever 
be  our  opinion  of  Professor  Lowell's  theory  of  their  develop- 
ment, there  is  no  doubt  that  Mars  is  relatively  a  much 
older  world  than  the  Earth,  and  that  we  see  in  it  a  world 
nearer  to  the  end  of  life  than  our  own,  although  relatively 
much  younger  than  the  Moon.  For,  as  has  been  well 
remarked,  "  in  space  there  are  both  cradles  and  tombs. 

Mars  has  two  satellites,  which  were  discovered  in  the 
memorable  year  1877.  For  forty  or  fifty  years  astronomers 
searched  for  satellites  to  the  red  planet.  It  was  felt  that 
as  the  Earth  had  one  satellite,  and  Jupiter  four,  Mars 
should  have  at  least  one,  if  not  two.  But  up  to  1877  the 
search  had  been  in  vain.  In  that  year,  however,  the  late 
Professor  Asaph  Hall,  aided  with  the  large  telescope  of 
the  Washington  Observatoiy,  detected  two  minute  little 
satellites  which  circle  round  the  red  planet.  In  several 
respects  these  little  satellites  differ  considerably  from  our 
satellite  the  Moon.  In  the  first  place,  the  Moon  is  com- 
paratively a  large  body.  These  satellites  of  Mars,  on  the 
other  hand,  are  very  small.  The  diameter  of  Phobos,  the 
nearer  of  the  two  to  Mars,  is  estimated  at  36  miles,  that 
of  Deimos,  the  more  distant,  at  10  miles.  In  the  second 
place  our  satellite  is  at  a  considerable  distance  from  the 
Earth— about  238,000  miles.  The  moons  of  Mars  are 
comparatively  close  to  their  primary.  Deimos  revolves  at 
a  distance  of  14,600  miles  ;  Phobos  at  a  distance  of  5800 
miles.  Thirdly,  our  Moon  is  a  leisurely  body.  It  requires 
about  27  days  to  complete  its  circuit  of  the  Earth.  The 
Martian  satellites  are  remarkable  for  the  extraordinary 
rapidity  of  their  motions.  Deimos,  the  more  distant  of 
the  two,  revolves  round  Mars  in  30  hours  18  minutes,  while 

95 


MARS— THE   RED  PLANET 

Phobos  completes  a  revolution  in  7  hours  39  minutes. 
Now  Mars  requires  over  24  hours  to  rotate  on  its  axis. 
Phobos  therefore  revolves  round  Mars  more  than  three 
times  in  one  Martian  day,  an  extraordinary  state  of  affairs. 
As  it  revolves  more  swiftly  than  the  planet  rotates,  it  will 
not,  like  our  Moon,  seem  to  rise  in  the  east  and  be  carried 
westward,  the  result  of  the  Earth^s  rotation  in  the  opposite 
direction.  This  Martian  satellite  rises  in  the  west,  and 
crosses  the  heavens  three  times  in  one  day.  It  overtakes 
Deimos  and  eclipses  it,  and  runs  through  all  its  phases  in 
eleven  hours.  Each  phase  lasts  only  three  hours.  Imagine 
a  world  with  a  Moon  which  could  be  seen  in  early  evening 
at  first  quarter,  and  three  hours  later  at  the  full.  The 
satellites  are  so  small,  however,  that  they  can  be  of  little 
use  to  Mars  in  illuminating  the  evening  skies. 

If  there  are  inhabitants  of  Mars,  their  skies  will  appear 
the  same  as  our  own.  The  stars  and  constellations  are 
identical,  but  of  course  the  different  bodies  of  the  solar 
system  are  differently  seen.  An  able  astronomical  writer 
explains  the  appearance  of  the  planets  from  Mars  in  the 
following  words  :  "  Jupiter  is  magnificent  from  Mars ;  it 
appears  to  the  Martians  half  as  large  again  as  it  seems  to 
us,  and  his  satellites  should  be  easily  visible  to  the  naked 
eye.  Saturn  is  likewise  very  brilliant,  Uranus  is  easily 
visible,  and  they  might  have  discovered  Neptune  before 
we  did.  They  must  have  distinguished  with  the  naked 
eye  a  large  number  of  the  small  planets  which  revolve 
between  their  orbit  and  that  of  Jupiter.  Mercury,  drawn 
closer  to  the  Sun,  and  lost  in  his  rays,  is  almost  impossible 
to  distinguish.  Venus  appears  to  them  as  Mercury  does 
to  us.  As  for  the  Earth,  how  do  they  see  it  ?  .  .  .  We 
are  for  that  planet  (Mars)  a  brilliant  star  presenting  an 
aspect  similar  to  that  which  Venus  presents  to  us  preceding 

96 


MARS— THE   RED   PLANET 

the  dawn,  and  following  the  twilight ;  in  a  word,  we 
are  to  the  inhabitants  of  Mars  the  shepherd^s  star.  Our 
natural  vanity,  then,  might  delude  us  with  the  idea  that 
the  inhabitants  of  Mars  contemplate  us  in  their  evening 
skies  purpled  with  the  last  solar  rays ;  that  they  admire 
us  from  afar ;  that  they  have  discovered  our  phases  and 
those  of  the  Moon  as  we  have  discovered  those  of  Venus 
and  Mercury ;  and  that  they  suppose  our  world  to  be  an 
abode  of  peace  and  happiness.  Perhaps,  even,  they  raise 
altars  to  us.  What  a  disillusion  if  they  could  observe  us 
a  little  nearer." 


97 


CHAPTER   IX 
THE    ASTEROIDS 

^  I  AHE  orbit  of  Mars  marks  the  limit  of  the  inner  group 
of  planets.  These  are  separated  from  the  outer 
group  by  what  is  variously  known  as  the  zone  of 
asteroids,  planetoids,  or  minor  planets.  They  are,  indeed, 
the  most  minute  of  bodies.  Unlike  their  mighty  neighbour 
Jupiter,  and  their  comparatively  large  neighbour  Mars,  they 
are  not  to  be  seen  without  the  aid  of  a  telescope.  The 
discovery  of  this  zone  belongs  therefore  to  comparatively 
recent  times,  although  the  existence  of  one  or  more  planets 
between  the  orbits  of  Mars  and  Jupiter  was  suspected  fully 
three  hundred  years  ago.  In  fact,  Kepler,  who  gave  to  the 
world  the  "  three  laws  "  of  planetary  motion,  predicted  that 
a  planet  would  be  found  revolving  between  the  two  bodies. 

Belief  in  the  existence  of  such  a  planet  was  strengthened, 
when,  in  1772,  a  German  astronomer  named  Bode  investi- 
gated a  curious  relationship,  since  known  as  Bode^s  Law, 
connecting  the  distances  of  the  planets.  If  we  write  down 
the  following  numbers,  of  which  each  after  the  second  is 
double  that  preceding  it— 0,  3,  6,  12,  24,  48,  and  96— 
and  add  four  to  each,  we  have  another  series — 4,  7,  10,  16, 
28,  52,  and  100.  Now  it  is  a  remarkable  fact  that  these 
numbers  represent  approximately  the  proportions  of  the 
distances  of  the  various  planets  from  the  Sun.  Bode 
pointed  out  that  4  corresponded  to  the  distance  of  Mercury, 
7  to  that  of  Venus,  10  to  that  of  the  Earth,  16  to  that  of 

98 


THE   ASTEROIDS 

Mars,  52  to  that  of  Jupiter,  and  100  to  that  of  Saturn. 
In  1781,  another  planet,  Uranus,  was  discovered,  and  it  was 
found  that  it  filled  the  number  196.  But  there  was  not 
a  planet  at  a  distance  corresponding  to  28  between  the 
orbits  of  Mars  and  Jupiter.  Bode  noted  this  fact,  and 
stated  his  belief  in  the  existence  of  a  planet  to  fill  the 
vacant  space.  In  1800,  Von  Zach,  another  German  investi- 
gator, summoned  a  congress  of  astronomers  to  make  a  search 
for  this  remarkable  body,  whose  existence  was  believed  in 
before  it  was  glimpsed  by  human  eye.  The  Zodiacal  region 
of  the  heavens  was  divided  for  the  purposes  of  the  search 
into  twenty-four  zones,  each  of  which  was  assigned  to  a 
particular  astronomer.  Some  astronomers  were  unaware 
of  the  fact  that  a  zone  of  the  heavens  had  been  laid  aside 
for  their  own  particular  attention.  Among  those  who  did 
not  at  the  end  of  1800  know  of  his  own  position  among 
the  band  of  searchers  was  Piazzi,  the  director  of  the 
Observatory  at  Palermo,  in  Sicily.  On  the  first  night 
of  the  nineteenth  century — January  1,  1801 — Piazzi  was 
making  observations  for  the  purpose  of  forming  a  star 
catalogue  when  he  noted  particularly  an  eighth  magnitude 
star.  On  the  following  night  he  ascertained  that  this  was 
not  one  of  the  stars  proper,  but  a  body  possessed  of  an 
appreciable  independent  motion.  At  first  Piazzi  believed 
that  he  had  discovered  merely  a  faint  comet,  but  he  soon 
came  to  the  conclusion  that  he  had  found  the  missing 
planet.  Accordingly  he  wrote  to  Bode  at  Berlin  informing 
him  of  his  discovery.  Piazzi  continued  to  observe  the 
strange  object  for  six  weeks  when  he  became  unwell.  By 
the  time  he  was  able  to  observe  again  the  planet  was  in- 
visible in  the  rays  of  the  sun,  and  astronomers  were  afraid 
that  it  had  been  found  only  to  be  lost.  However,  an  orbit 
was  calculated  from  the  few  observations  made  by  Piazzi, 

99 


THE  ASTEROIDS 

and  on  the  last  day  of  1801  the  planet  was  again  observed. 
It  received  the  name  of  Ceres  at  the  suggestion  of  the 
discoverer. 

The  gap  had  now  beejn  filled.  The  planet,  it  was  true, 
was  not  comparable  in  size  with  any  of  the  known  planets 
of  the  solar  system.  It  was  so  faint  as  to  be  invisible  to 
the  unaided  eye.  Still,  astronomers  believed  that  the 
missing  planet  had  been  found,  filling  the  vacant  space  28 
of  Bode's  numerical  progression.  The  solar  system  was  now 
regarded  as  complete.  Only  three  months  after  Ceres  was 
rediscovered  this  opinion  was  rudely  overturned.  Gibers, 
a  famous  German  astronomer,  followed  closely  the  new 
planet  Ceres  in  the  months  following  its  rediscovery,  and  on 
March  28, 1802,  he  was  astonished  to  find  quite  close  to  the 
position  of  Ceres  another  strange  star  of  the  eighth  magni- 
tude. A  few  hours  showed  him  that  this  object  was  in 
motion.  Here  was  a  remarkable  discovery.  Not  one,  but 
two  planets,  revolved  in  the  vacant  space ;  and  the  new 
body — which  received  the  name  of  Pallas — was  found  to 
revolve  round  the  Sun  at  nearly  the  same  distance  as  Ceres. 
The  two  bodies  were  without  doubt  akin  to  each  other.  The 
symmetry  of  the  solar  system  was  supposed  to  be  broken, 
and  no  one  was  more  astounded  at  the  existence  of  two 
planets  where  one  alone  was  expected,  than  Olbers,  the 
discoverer  of  Pallas.  At  length  he  put  forward  his  expla- 
nation of  the  presence  of  two  small  bodies.  He  supposed 
that  there  had  existed  between  the  orbits  of  Mars  and 
Jupiter  a  large  planet,  of  a  kind  similar  to  the  other  worlds 
of  the  solar  system,  and  that,  through  some  terrific  catas- 
trophe, this  planet  had  in  the  remote  past  been  shattered 
to  fragments.  He  predicted  that  many  more  such  frag- 
ments as  Ceres  and  Pallas  were  likely  to  be  found,  and 
recommended  that  a  search  be  made  for  other  portions.  In 

100 


THE   ASTEROIDS 

1 804,  Harding,  another  German  astronomer,  discovered  a 
third  fragment,  which  was  named  Juno ;  aodatir/ISO^Olbers,; 
who  had  been  maintaining  a  close  watcl\,  detected  a/qiirth,^ 
The  new  planet  was  named  Vesta,  and  r^  file  ]bf igjitfet; 
though  not  the  largest,  of  the  asteroids.    These  four  bodies 
were  named  the  asteroids  or  planetoids,  and  for  about  forty 
years  the  system  was  again  regarded  as  complete.     It  may 
be  stated  here  that  the  theory  of  Olbers,  although  it  led 
to  the  discovery  of  other  two  "fragments,"  is  not  now 
accepted  by  astronomers. 

As  no  further  asteroids  seemed  to  be  forthcoming,  the 
search  was  abandoned  in  1816.  Fourteen  years  later, 
however,  it  was  resumed.  A  German  amateur  astronomer, 
Hencke,  ex-postmaster  of  Driessen,  in  Prussia,  began  to 
search  for  further  members  of  the  asteroid  system.  For 
fifteen  years  he  watched  without  success.  But  at  last, 
in  December  1845,  he  discovered  a  fifth  asteroid,  which 
received  the  name  of  Astraea.  A  year  and  a  half  later 
he  detected  yet  another,  known  as  Hebe.  In  the  same 
year  an  English  astronomer,  Hind,  detected  Iris  and 
Flora,  other  two  members  of  the  system.  Since  1847 
not  a  single  year  has  passed  without  the  discovery  of 
one  or  more  asteroids.  Some  astronomers  devoted 
almost  all  their  time  to  the  search  for  and  discovery 
of  minor  planets.  Peters,  an  American  astronomer,  dis- 
covered forty-eight.  Palisa,  an  astronomer  of  Vienna, 
found  over  eighty,  while  Goldschmidt,  Luther,  Chacor- 
nac,  and  other  observers  each  discovered  many  of 
these  small  planets.  The  method  of  discovery  adopted 
by  these  astronomers  was  to  construct  charts  of  the 
regions  round  about  the  ecliptic  in  which  such  planets 
were  likely  to  be  found,  and  to  compare  those  charts 
with  the  actual  appearance  of  these  regions  of  the 

101 


THE  ASTEROIDS 

heavens  through  the  telescope.  By  this  method  it  was 
easy  to  «pick-:out  unfamiliar  stars  and  identify  them  as 
new  asteroids.  This  method,  however,  has  now  been 
discarded.  A  new  method  was  devised  in  1891  by 
Professor  Max  Wolf  of  Heidelberg,  who  has  discovered 
over  a  hundred  asteroids.  It  occurred  to  Dr.  Wolf  to 
apply  photography  to  the  detection  of  these  objects.  It 
is  obvious  that  an  asteroid,  owing  to  its  appreciable 
motion,  will  be  represented  on  a  photographic  plate  not 
as  a  point  of  light  like  the  stars  in  the  background,  but 
as  a  streak  of  appreciable  length.  As  Professor  Brashear 
explains :  "  When  the  picture  is  developed,  the  stellar 
images  show  themselves  as  small  circular  dots,  but  if  a 
planet  were  in  the  photographic  field  during  the  ex- 
posure, its  image  would  be  that  of  a  very  short  line  or 
trail  about  one-twentieth  of  an  inch  long,  because  it  has 
an  average  movement  through  space  of  a  little  less  than 
half  the  diameter  of  the  Moon  in  twenty-four  hours, 
while  the  stars  remain  practically  stationary.  This  tiny 
trail  is  the  clue  to  a  new  planet,  or  perhaps  one  already 
discovered."  Since  1891  this  method  has  been  used 
extensively.  In  less  than  two  years  Dr.  Wolf  discovered 
seventeen  asteroids.  During  the  past  eighteen  years 
many  minor  planets  have  been  detected  in  this  way  by 
Wolf  and  his  assistants,  and  by  Charlois,  Metcalf,  and 
other  observers.  The  number  of  known  asteroids  now 
stands  at  about  seven  hundred. 

By  the  time  Dr.  Wolf  applied  his  photographic  method 
popular  interest  in  the  ever-increasing  family  of  little 
planets  was  on  the  wane.  Mr.  G.  F.  Chambers  in  1895 
described  the  asteroids  as  "of  very  little  interest  to 
any  body. "  It  was  hinted  that  there  was  no  use  con- 
tinuing a  search  for  bodies  which  so  closely  resembled 

102 


THE   ASTEROIDS 

each  other,  and  the  discovery  of  which  served  no  useful 
purpose  to  the  discoverer.  Certainly,  it  must  have  been 
a  singularly  uninteresting  search  for  the  astronomers  who 
prosecuted  it,  because  with  so  many  asteroids  already 
discovered  there  was  always  the  possibility  that  the  newly 
found  object  might  not  be  a  new  asteroid  at  all,  but 
merely  a  known  one  which  had  been  lost  to  astronomers. 
Great  care  had  to  be  taken  to  insure  that  the  same 
planet  was  not  "  discovered "  twice  and  regarded  as  two 
different  objects.  As  Professor  Turner,  of  Oxford,  re- 
marks :  "  There  was  a  system  of  numbering  in  existence 
as  well  as  of  naming,  but  it  was  inadvisable  to  attach 
even  a  number  to  a  planet  until  it  was  quite  certain  that 
the  discovery  was  new,  for  otherwise  there  might  be  gaps 
created  in  what  should  be  a  continuous  series  by  spurious 
discoveries  being  struck  out.  Accordingly  it  was  decided 
to  attach  at  first  to  the  object  merely  a  letter  of  the 
alphabet,  with  the  year  of  discovery  as  a  provisional 
name.  The  alphabet,  however,  was  run  through  so 
quickly,  and  confusion  was  so  likely  to  ensue  if  it  was 
merely  repeated,  that  on  recommencing  it  the  letter  A 
was  prefixed,  and  the  symbols  adopted  were  therefore 
AA,  AB,  AC,  &c.  After  completing  the  alphabet  again 
the  letter  B  was  prefixed,  and  so  on."  This  was  getting 
tiresome  to  the  astronomical  world,  until  at  length  in 
1898  an  insignificant  little  object  was  discovered  on  a 
photographic  plate  by  Witt  in  Berlin,  and  designated 
as  D.Q.  It  was  seen  that  this  was  a  real  discovery,  and 
to  the  little  body  was  assigned  the  number  433,  and  the 
name  of  Eros.  It  soon  appeared  that  this  asteroid  was 
of  more  interest  and  use  to  the  astronomer  than  all  the 
other  asteroids  put  together.  The  vast  majority  of  the 
asteroids  have  their  orbits  between  the  paths  of  Mars 

103 


THE   ASTEROIDS 

and  Jupiter,  but  this  little  planet  revolves  in  an  orbit 
so  elliptical  that  at  its  nearest  position  to  the  Earth  it 
comes  within  the  orbit  of  Mars,  and  is  only  13^  millions 
of  miles  from  the  Earth.  It  is  at  times  our  nearest 
planetary  neighbour,  but  is  so  faint  that  it  is  never  to 
be  seen  without  the  aid  of  a  telescope.  It  can,  however, 
be  photographed,  and  in  this  way  is  of  the  greatest  use 
to  the  astronomer.  By  means  of  observations  on  a  body 
so  near,  its  distance,  and  thus  the  scale  of  the  whole 
solar  system,  is  very  easily  calculated.  The  little 
planetoid  therefore  has  supplied  astronomers  with  perhaps 
the  most  reliable  measurements  of  the  actual  scale  of  the 
solar  system.  Since  1898  the  discovery  of  asteroids  has 
gone  on  at  the  same  rate,  but  no  further  objects  of 
interest  have  been  found. 

Although  the  asteroids  are,  generally  speaking,  akin  to 
one  another,  and  form  a  distinct  zone  in  the  solar  system, 
they  have  their  own  individual  differences.  Their  periods 
of  revolution  vary  considerably  from  about  three  to  nine 
years.  Some  of  the  orbits  are  very  elliptical  in  shape, 
and,  unlike  the  large  planets,  many  of  them  do  not  move 
almost  exactly  in  the  plane  of  the  ecliptic.  Pallas,  for 
instance,  moves  in  a  path  which  is  inclined  to  the 
ecliptic  at  an  angle  of  thirty-four  degrees.  In  size,  also, 
there  are  great  differences.  The  four  earlier  discovered 
asteroids — Ceres,  Pallas,  Vesta,  and  Juno — are  the  largest. 
These  are  the  only  asteroids  which  actually  show  measur- 
able discs  and  can  thus  be  actually  measured,  and  it  is 
only  by  the  aid  of  the  largest  telescopes  in  the  world 
that  such  measurement  can  be  made.  Ceres  is  477  miles 
in  diameter,  Pallas  304  miles,  Vesta  239  miles,  and 
Juno  120  miles.  Vesta  is  the  brightest  of  the  four,  so 
its  surface  must  be  highly  reflective.  The  sizes  of  the 

104 


THE   ASTEROIDS 

smaller  planets  have  not  been  measured,  but  can  be 
estimated,  and  it  is  believed  that  few  of  them  have  a 
greater  diameter  than  twenty-five  miles.  Practically 
nothing  is  known  of  the  physical  nature  of  these  minute 
planets.  Professor  Barnard  observed  the  four  larger  ones 
carefully  some  years  ago  with  the  large  telescope  of  the 
Lick  Observatory,  and  saw  no  traces  of  atmosphere  round 
them.  Nothing  is  known  either  of  their  rotation  or  of 
the  actual  condition  of  their  surfaces.  Some  of  them  are 
variable  in  light,  and  it  is  supposed  that  such  variation  is 
caused  by  the  different  reflective  powers  of  the  different 
hemispheres,  combined  with  the  rotation  of  the  planetoids 
on  their  axes.  These  variable  asteroids  probably  have 
rugged  surfaces  on  which  the  amount  of  light  reflected 
varies  considerably. 

The  asteroid  group  is  one  of  the  most  remarkable 
features  in  the  solar  system.  It  is  obvious  that  one 
large  planet  is  replaced  by  many  little  ones ;  it  is  also 
obvious  that  the  zone  divides  the  two  groups  of  Inner 
Planets  and  Outer  Planets,  and  thus  separates  the  solar 
system  into  two  portions.  The  existence  in  the  solar 
system  of  this  group  of  minute  bodies  all  but  innumerable, 
each  pursuing  its  own  appointed  path  round  the  orb  of 
day,  is  another  example  of  the  variety  and  harmony  of 
Nature.  • 


105 


CHAPTER   X 
JUPITER,   THE   GIANT   PLANET 

ONCE  in  about  every  thirteen  months  there  reaches 
the  meridian  at  midnight  one  of  the  most  brilliant 
objects  in  the  sky.  Rising  about  sunset  in  the 
east,  it  gradually  ascends  until  it  is  due  south  at  midnight 
and  in  "  opposition  "  to  the  Sun.  For  some  time  after 
opposition  it  is  the  most  brilliant  object  in  the  night 
skies,  and  as  such  commands  the  attention  of  even  the 
most  casual  of  star-gazers.  For  Jupiter  so  far  outshines 
all  the  stars  in  its  vicinity  that  there  can  be  no  doubt 
in  identifying  the  great  planet.  It  reigns  supreme,  shin- 
ing with  a  steady  light,  not  so  soft  as  that  of  Venus, 
but  sharper  and  more  sparkling.  As  Flammarion  re- 
marks :  "  When  Jupiter  shines  among  the  stars  of  the 
silent  night,  and  when  our  gaze  is  fixed  on  him,  who 
would  suppose,  while  admiring  this  simple  luminous 
point,  that  it  is  an  enormous  and  massive  globe,  weighing 
over  three  hundred  times  more  than  the  planet  which 
we  inhabit,  and  of  which  the  colossal  volume  exceeds  by 
nearly  thirteen  hundred  times  that  of  the  Earth  ?  We 
have  our  eyes  fixed  on  him,  his  light  is  so  vivid  that  it 
casts  a  shadow  like  that  of  Venus,  but  we  do  not  guess 
the  marvellous  grandeur  of  this  distant  body.1'  Of  all 
the  planets  Jupiter  is  the  easiest  to  observe  telescopically. 
The  smallest  instrument  will  show  that  it  is  a  planet 
with  a  round  disc,  and  will  give  us  a  glimpse  of  the  four 
satellites  of  the  planet  discovered  by  Galileo  in  1610, 
over  three  hundred  years  ago.  Great  must  have  been 

106 


JUPITER,  THE   GIANT  PLANET 

the  delight  and  wonder  of  the  great  Italian  astronomer 
when,  pointing  his  newly  constructed  telescope  to  Jupiter 
for  the  first  time,  he  beheld  the  luminous  point  of  light 
transformed   into  a  flat   disc,  with  four  little   points  of 
light  circling  around  it.     A  two-inch  telescope  gives  a 
very  striking  view  of  the  planet.      On  a  clear  night  such 
an  instrument  enables  us  to  see  on  the  disc  two  or  three 
parallel  strokes,  as  it  were.     This  is  our  first  glimpse  of 
the  famous  belts  of  Jupiter,  which  were  first  discovered 
after  the  time  of  Galileo.     It  requires  a  much  larger 
instrument  to  bring  out  the  principal  features  of  the 
belts.     With   a  good   telescope   we   may   view   what    an 
American  astronomer  thus   vividly  describes :    "  Belts  of 
reddish    clouds,    many    thousands    of   miles    across,    are 
stretched  along  on  either  side  of  the  equator  of  the  great 
planet ;  the  equatorial  belt  itself  brilliantly  lemon-hued, 
or  sometimes  ruddy,  is  diversified  with  white  globular  and 
balloon-shaped  masses,  which  almost  recall  the  appearance 
of  summer  cloud  domes  hovering  over  a  terrestrial  land- 
scape,   while    towards    the    poles    shadowy    expanses    of 
gradually  deepening  blue  or  blue-grey  suggest  the  com- 
parative coolness  of  those  regions  which  lie  always  under 
a  low  Sun."     The  belts  are  not  permanent  markings ; 
they  are  belts  of  cloud,   and   as   such   are   continually 
changing.     Still,  they  are  not  so  fleeting  as  the  clouds 
in  our  own  atmosphere.     Some  of  the  Jovian  features, 
indeed,  are  more  or  less  permanent.     Chief  among  these 
must  be  mentioned  an  object  known  as  "  the  great  red 
spot."     It  was  first  noticed  by  a  number  of  observers  in 
the  summer  of  1878,  and  described  by  them  as  a  pale 
pinkish,    oval    spot.      In    1879   it   became    much    more 
prominent.     The  pinkish  hue  gave   place   to  brick-red, 
while  the  entire  object  extended  30,000  miles  from  east 

107 


JUPITER,   THE   GIANT  PLANET 

to  west,  and  7000  from  north  to  south.  The  area  of  the 
spot  was  no  less  than  200  million  square  miles,  greater 
than  the  area  of  the  entire  terrestrial  globe.  For  three 
years  the  spot  was  a  brilliant  object,  the  most  prominent 
feature  on  the  globe  of  Jupiter,  lying  immediately  south 
of  the  great  equatorial  belt  of  the  planet.  Then  it  began 
to  fade,  and  an  observation  by  Ricco  at  Palermo  in  1883 
was  thought  to  be  the  last.  But  in  a  short  time  it 
revived  and  again  became  the  most  prominent  object  on 
the  planet's  disc.  Again  it  faded  considerably,  but  it  is 
still  visible,  a  permanent  feature  of  Jupiter's  disc. 

This  marvellous  spot  has  for  many  years  attracted  the 
attention  of  astronomers  all  over  the  world.  Many  specula- 
tions have  been  made  as  to  its  nature,  and  it  is  difficult  to 
ascertain  the  exact  cause  of  the  appearance  in  a  cloudy 
atmosphere  of  a  permanent  feature  lasting  so  many  years. 
Mr.  W.  F.  Denning,  one  of  the  most  devoted  observers  of 
the  planet,  gives  as  his  opinion  "  that  it  represents  an 
opening  in  the  atmosphere  of  Jupiter  through  which  in 
1878-82  we  saw  the  dense  red  vapours  of  his  lower  strata, 
if  not  his  actual  surface  itself.  Its  lighter  tint  in  recent 
years  is  probably  due  to  the  filling  in  of  the  cavity  by  the 
encroachment  of  durable  clouds  in  the  vicinity."  Another 
remarkable  fact  in  connection  with  the  spot  was  ascertained 
by  the  American  astronomer  Professor  Barnard.  "  One  of 
the  most  interesting  features  of  the  great  spot,"  he  said, 
"  was  the  repulsion  it  seemed  to  exert  upon  adjacent  mark- 
ings on  the  planet.  For  a  time  it  was  surrounded  by  a  sea 
of  light  that  completely  encircled  it  for  a  distance  of  three 
or  four  thousand  miles,  and  which  appeared  as  a  visible 
barrier  against  the  approach  of  any  spot  or  marking." 

Observations  on  various  spots  and  belts  many  years 
ago  revealed  the  fact  that  Jupiter  rotated  on  its  axis 

108 


JUPITER,  THE   GIANT  PLANET 

in  a  little  under  ten  hours.  The  most  exact  determination 
fixes  the  rotation  period  at  9  hours  55  minutes  36 '56 
seconds.  Thus  Jupiter's  "day"  is  very  much  shorter 
than  that  of  the  Earth,  notwithstanding  the  size  of  the 
mighty  planet.  The  curious  point,  however,  about  the 
rotation  of  Jupiter,  as  ascertained  from  observations  on  the 
red  spot  and  other  markings,  is  that,  like  the  Sun,  its 
rotation  is  not  uniform.  According  to  one  astronomer, 
no  fewer  than  nine  different  rotation  periods  are  found. 
There  is  not  much  difference,  it  is  true,  between  the 
various  periods,  but  this  difference  gives  rise  to  curious 
results.  Some  bright  spots  round  about  the  equator 
actually  overtake  the  red  spot  at  the  rate  of  260  miles  an 
hour.  All  these  facts  go  to  prove  that  in  Jupiter  we  have 
a  world  of  a  different  type  from  the  four  inner  planets. 
In  the  case  of  Mars,  for  instance,  we  see  the  actual  surface 
of  the  planet.  The  markings  may  change  in  accordance 
with  the  seasons,  but  they  are  always  to  be  seen,  and  the 
rotation  period  derived  from  them  is  constant  and  un- 
changing. In  the  case  of  Jupiter  we  never  see  the  actual 
surface.  A  remarkable  thick  atmosphere  enshrouds  the 
planet,  an  atmosphere  quite  unlike  our  own.  We  cannot 
compare  the  Jovian  markings  to  our  terrestrial  clouds.  A 
cloud  on  the  Earth  is  a  fleeting  thing.  It  does  not  last 
for  days,  still  less  for  thirty-two  years.  The  red  spot  in 
Jupiter's  atmosphere  has  been  seen  since  1878. 

It  is  quite  obvious,  therefore,  that  Jupiter  is  a  body 
of  quite  a  different  order  from  our  own  world.  In  many 
ways  it  resembles  the  Sun  more  than  the  smaller  planets. 
Indeed,  in  1879,  Bredikhine  of  Moscow  observed  on  the 
Jovian  disc  a  group  of"  faculae  "  similar  to  those  of  the  Sun. 
Some  astronomers  believed  that  the  markings  on  Jupiter, 
like  those  on  the  Sun,  are  regulated  by  an  eleven-year  period, 

109 


JUPITER,   THE   GIANT   PLANET 

but  this  is  not  absolutely  certain.  At  all  events,  observa- 
tions of  Jupiter  during  the  last  fifty  years  have  abundantly 
shown  that  it  resembles  the  Sun  more  than  the  Earth. 

It  used  to  be  believed  that  the  atmosphere  was  some- 
thing similar  to  our  own,  but  much  more  dense,  and  that 
the  cloud  belts  were  analogous  to  the  trade  winds  on  our 
planet.  But  the  impossibility  of  this  view  was  long  since 
demonstrated.  The  clouds  on  the  Earth  are  raised  by 
Sun  heat.  Jupiter  is  at  a  much  greater  distance  from 
the  Sun  than  the  Earth  is,  and  yet  it  possesses  an 
atmosphere  much  more  dense  and  cloudy  than  ours.  The 
explanation  is  obvious — Jupiter  is  very  much  larger  than 
the  Earth ;  it  is  a  world  in  a  state  of  chaos,  "  without 
form  and  void  "  ;  it  is  in  a  condition  of  great  heat,  so  that 
the  vapours,  instead  of  settling  on  the  surface  in  the  form 
of  oceans,  are  boiled  off*  the  fiery  surface,  as  it  were,  and 
kept  suspended  in  the  atmosphere  in  the  form  of  dense 
cloud  masses.  Jupiter  seems  to  be  in  a  very  primitive 
condition,  somewhat  similar  to  Saturn,  and  probably 
Uranus  and  Neptune,  and  it  throws  an  interesting  side- 
light on  the  previous  condition  of  our  own  world. 

For  some  time  astronomers  believed  Jupiter  to  be 
slightly  self-luminous,  but  this  view  has  not  been  con- 
firmed. The  planet  probably  gives  out  an  appreciable 
quantity  of  heat,  but  it  is  likely  that  its  days  of  shining 
by  its  own  light  are  ended.  Very  probably  the  surface  is 
only  now  becoming  solidified,  and  enormous  volcanic  dis- 
turbances are  of  daily  occurrence  in  the  semi-liquid  planet. 
Of  course  this  is  but  speculation,  for  the  atmosphere  is  so 
dense  that  it  is  quite  impossible  to  see  it.  From  the 
surface  of  the  planet — whether  it  is  a  solid  or  a  semi- 
liquid  surface — no  glimpse  of  the  outer  universe  is  visible. 
Supposing,  however,  that  an  observer  on  Jupiter  could 

110 


JUPITER,  THE   GIANT  PLANET 

see  through  the  cloud  belts,  the  Earth  would  be  hardly 
visible,  being  only  seen  with  difficulty  in  the  vicinity  of 
the  Sun.  "  At  night,"  says  a  famous  astronomer,  "  the 
spectacle  of  the  sky  seen  from  Jupiter  is,  with  reference 
to  the  constellations,  the  same  as  that  which  we  see  from 
the  Earth.  There,  as  here,  shine  Orion,  the  Great  Bear, 
Pegasus,  Andromeda,  Gemini,  and  all  the  other  constella- 
tions, as  well  as  the  diamonds  of  our  sky.  The  390 
millions  of  miles  which  separate  us  from  Jupiter  in  no 
way  alter  the  celestial  perspectives.  The  most  curious 
spectacle  of  this  sky  is  unquestionably  the  spectacle  of  the 
four  moons.1'  To  these  moons  Jupiter  acts  as  a  miniature 
Sun,  giving  out  an  appreciable  amount  of  heat  as  well  as 
reflecting  the  heat  of  the  Sun.  Jupiter  is  attended  by  no 
fewer  than  eight  satellites,  four  large  and  four  small.  The 
discovery  of  the  four  large  satellites  was  one  of  the 
greatest  in  the  history  of  astronomy.  In  1610,  Galileo, 
at  Padua,  turned  the  newly-invented  telescope  on  Jupiter, 
and  discovered  that  the  giant  planet  was  surrounded  by 
four  satellites.  The  discovery  was  hailed  with  great  joy 
by  the  supporters  of  the  Copernican  system.  Here  was 
a  miniature*  of  the  solar  system  disclosed  by  Galileo's 
telescope,  which  ought  to  convince  even  the  most  sceptical. 
But  the  opponents  of  the  new  system  would  not  be 
convinced,  and  regarded  the  discoverer  with  very  un- 
friendly feelings.  One  Italian  student  refused  to  look 
through  the  telescope  lest  he  should  see  the  satellites. 
Another  consented  to  observe  Jupiter,  and  was  immediately 
convinced  that  the  satellites  existed ;  while  a  third  de- 
clared that  even  though  he  saw  the  satellites  through  the 
telescope  he  would  not  believe  in  them,  declaring  that 
they  were  in  the  telescope  and  not  in  the  sky. 

The  four  satellites  are  sometimes  known  by  the  name 
111 


JUPITER,   THE   GIANT  PLANET 

of  lo,  Europa,  Ganymede,  and  Callisto,  though  they  are 
more  frequently  designated  by  the  numerals  L,  II.,  III., 
and  IV.  The  nearest  satellite,  lo,  revolves  round  Jupiter 
in  1  day  18  hours  27  minutes,  at  a  mean  distance  of 
261,000  miles.  Its  diameter  measures  about  2500  miles. 
The  second  satellite,  Europa,  the  smallest  of  the  four,  with 
a  diameter  of  2100  miles,  revolves  round  the  primary  in 
3  days  13  hours  13  minutes,  at  a  mean  distance  of  415,000 
miles.  The  third  moon,  Ganymede,  is  the  largest  of  the 
four,  its  diameter  measuring  3550  miles.  It  is,  therefore, 
larger  than  the  planet  Mercury.  It  moves  round  Jupiter 
in  7  days  3  hours  42  minutes,  at  a  mean  distance  of 
664,000  miles.  Callisto,  the  fourth  satellite,  with  a 
diameter  of  2960  miles,  revolves  round  the  primary  at  a 
mean  distance  of  1,167,000  miles  in  16  days  16  hours 
32  minutes. 

These  satellites  are  among  the  easiest  objects  of  obser- 
vation to  the  amateur  astronomer.  The  smallest  telescopes 
will  show  them,  and  they  are  a  source  of  never  ending 
pleasure.  They  may  be  seen  sometimes  in  transit  across 
the  disc  of  Jupiter,  while  sometimes  we  are  able  to  witness 
their  immersion  in  the  shadow  of  the  giant  planet  and 
consequent  eclipses,  while  at  times  we  see  Jupiter's  disc 
pass  over  one  or  more  of  the  satellites  and  obscure  them 
from  view.  This  phenomenon  is  known  technically  as  an 
"  occultation." 

A  small  telescope  will  not  show  surface  markings  on 
the  discs  of  the  satellites.  Even  with  the  largest  and  best 
instruments,  astronomers  have  learned  little  of  the  consti- 
tution of  these  moons.  As  to  size,  the  two  largest  are  of 
planetary  bulk  and  dimensions.  The  four  satellites  com- 
bined form  one  6000th  part  of  the  mass  of  Jupiter,  and 
their  volumes  form  one  7600th  part  of  the  volume  of  the 

112 


JUPITER,   THE   GIANT   PLANET 

giant  planet.  Hence  we  see  that  while  three  of  the  satel- 
lites are  absolutely  larger  than  our  Moon,  all  four  are,  in 
comparison  to  Jupiter's  bulk,  relatively  much  smaller 
bodies.  The  satellites  seen  from  Jupiter's  surface  cover 
an  area  of  the  sky  larger  than  the  area  filled  by  our  Moon, 
but  they  are  much  less  brilliantly  illuminated,  owing  to 
the  much  greater  distance  of  the  Jovian  system  from  the 
Sun.  The  total  amount  of  light  reflected  from  all  four 
satellites  at  once  is  only  one-sixteenth  of  that  reflected  by 
the  full  Moon  as  seen  from  the  surface  of  the  Earth. 

For  over  280  years  the  system  of  Jupiter  was  regarded 
as  complete.  The  four  satellites  had  been  known  for  a 
long  period,  their  motions  had  been  carefully  calculated ; 
in  fact,  astronomers  were  thoroughly  acquainted  with  all 
the  details  of  the  Jovian  system.  Great  was  the  surprise 
among  astronomers  when  in  September  1892  it  was  an- 
nounced that  an  American  astronomer  had  discovered  a 
fifth  satellite.  On  the  ninth  of  that  month  Professor 
Barnard,  while  observing  Jupiter  with  the  great  telescope 
of  the  Lick  Observatory  in  California,  detected  a  minute 
speck  of  light  near  the  planet.  A  series  of  observations 
proved  that  this  was  indeed  a  new  satellite  of  Jupiter,  closer 
to  the  planet  than  any  of  the  other  moons.  It  revolves 
round  Jupiter  in  1 1  hours  57  minutes,  at  a  mean  distance 
of  112,000  miles.  It  is  very  much  smaller  than  the  other 
satellites,  for  its  diameter  is  little  over  a  hundred  miles. 

In  1905  two  other  satellites  of  Jupiter  were  discovered 
by  Professor  Perrine  at  the  same  Observatory.  Both  of 
these  minute  objects  were  discovered  by  the  aid  of  the 
photographic  plate.  The  sixth  satellite  revolves  round 
Jupiter  in  242  days,  at  a  mean  distance  of  6,968,000 
miles.  The  seventh  satellite  is  slightly  closer  to  the  planet, 
round  which  it  moves  in  200  days,  at  a  mean  distance  of 

113  H 


JUPITER,  THE   GIANT  PLANET 

6,136,000  miles.  Early  in  1908  came  the  announcement 
of  the  discovery  of  another  satellite.  The  eighth  moon, 
also  very  small  and  faint,  was  discovered  by  Mr.  Melotte, 
assistant  at  the  Royal  Observatory,  Greenwich,  with  the 
aid  of  photography.  It  is  at  a  much  greater  distance 
from  the  planet  than  the  other  satellites,  and  revolves 
round  Jupiter  in  the  opposite  direction.  In  astronomical 
language  its  motion,  instead  of  being  direct,  is  retrograde. 
In  this  respect  the  most  distant  satellite  of  Jupiter  re- 
sembles the  most  distant  satellite  of  Saturn,  as  will  be 
explained  in  the  next  chapter.  It  is  quite  possible  that 
there  may  be  other  satellites  still  undiscovered. 

The  system  of  Jupiter  is  as  interesting  as  it  is  beautiful. 
So  far  as  is  known  at  present,  the  planet  has  eight  satellites, 
four  of  almost  planetary  dimensions,  four  of  what  may  be 
called  asteroidal  size.  The  system  is  more  beautiful  and 
complex  than  Galileo  and  the  earlier  astronomers  imagined. 
As  to  the  possibility  of  life  in  the  Jovian  system,  the 
reader  will  have  been  able  to  judge  from  the  physical 
condition  of  the  planet  that  no  life,  akin  to  life  as  we 
know  it,  can  possibly  exist  at  the  present  moment.  That 
it  may  be  inhabited  at  some  future  time  when  the  cloud 
belts  roll  away,  and  the  vapours  settle  on  the  surface  as 
oceans,  is  quite  possible.  Some  astronomers  believe  that 
the  satellites  are  likely  to  be  inhabited,  and  certainly  the 
four  larger  moons  seem  the  more  likely  bodies  in  the 
Jovian  system  on  whose  surfaces  life  may  exist.  To  these 
moons  Jupiter  will  be  a  semi-sun  radiating,  if  little  or 
no  inherent  light,  at  least  a  vast  amount  of  inherent  heat. 
But  of  the  actual  surfaces  of  the  satellites  we  know  practi- 
cally nothing.  Marvellous  and  complex  as  is  the  system 
of  Jupiter,  it  is  simple  compared  to  that  of  Saturn,  to  the 
consideration  of  which  the  next  chapter  is  devoted, 

114 


CHAPTER   XI 
SATURN,   THE   RINGED   WORLD 

IN  ancient  days  when  astrology  had  sway  over  mankind, 
the  planets  were  believed  to  influence  the  destinies  of 
mortals.  To  be  born  under  the  planet  Jupiter  was 
to  be  sure  of  a  career  marked  by  good  fortune  and  dis- 
tinguished by  glory.  Mars  was  the  god  of  war,  and  those 
born  under  the  sign  of  that  planet  were  characterised  by 
martial  deeds  and  military  renown.  The  favourites  of 
Mercury  had  the  arts  as  their  special  sphere,  while  Venus 
held  sway  in  the  realms  of  love.  Saturn  was  known  as  the 
unlucky  planet.  Its  slow  motion  and  its  dull  leaden  light 
betokened  gravity  and  gloom,  and  those  born  under  its 
sign  were  called  "  saturnine,"  and  were  thought  to  be  dull 
and  morose  in  their  natures,  and  to  be  destined  to  grief 
and  calamity.  To  the  unaided  eye  Saturn  appears  as  a 
star  of  the  first  magnitude,  with  none  of  the  brilliancy  of 
the  other  planets.  It  has  nothing  of  the  steady  brilliance 
of  Jupiter,, the  soft  luminosity  of  Venus,  or  the  fiery  red 
light  of  Mars.  Consequently  the  ancients  thought  Saturn 
by  far  the  least  interesting  of  the  planets,  and  indeed,  when 
it  is  examined  with  the  unaided  eye,  we  are  inclined  to 
accept  their  opinion.  But  with  a  powerful  telescope  we 
gain  quite  a  different  idea  of  Saturn.  So  far  from  being 
the  least  interesting  of  the  planets,  it  is  the  most  interest- 
ing. Indeed,  it  is  absolutely  unique  in  the  solar  system, 
and  so  far  as  is  known,  in  the  Universe. 

115 


SATURN,  THE   RINGED   WORLD 

When  we  turn  the  telescope  on  it  we  behold  a  glorious 
orb.  Its  disc  is  striped  with  belts  similar  to  those  of  Jupiter, 
only  fainter  owing  to  its  greater  distance.  A  wonderful 
system  of  three  rings  surrounds  the  planet — two  bright, 
and  one  of  a  dusky  hue.  These  are  perfect  in  symmetry 
and  exquisite  in  beauty.  Our  sense  of  the  marvellous  is 
deepened  when  it  is  borne  in  mind  that  these  rings  are  not 
less  than  176,000  miles  in  diameter  and  30,000  miles  in 
width,  and  not  more  than  from  fifty  to  one  hundred  miles 
in  thickness.  Telescopic  contemplation  of  this  magnificent 
planet,  with  its  imposing  system  of  rings,  fills  the  mind 
with  feelings  of  wonder  and  awe.  As  Flammarion  puts 
it :  "  When  we  think  that  there  is  here  a  celestial  deck  on 
which  the  entire  globe  of  the  Earth  might  roll  like  a  ball 
on  a  road,  and  that  the  world  poised  in  the  centre  is 
several  hundred  times  larger  than  our  planet,  we  transport 
ourselves  easily  in  thought  to  those  sublime  regions."" 

The  system  of  rings  which  encircle  Saturn  has  been 
known  to  astronomers  for  two  and  a  half  centuries.  To 
Galileo  they  were  a  source  of  much  perplexity.  His 
telescope  was  not  powerful  enough  to  disclose  their  true 
nature.  When  he  first  observed  Saturn  it  seemed  to  him 
to  be  oval-shaped,  and  this  appearance  he  believed  to  be 
due  to  the  fact  that  the  planet  was  in  reality  triple,  con- 
sisting of  a  large  central  body  with  a  smaller  orb  on  each 
side,  "  like  two  servants  who  help  old  Saturn  on  his  way." 
Accordingly,  he  announced  that  the  planet  was  triple. 
Some  time  later  he  concluded  that  the  appearance  pointed 
to  the  existence  not  of  a  triple  planet,  but  of  an  orb  oval 
in  shape.  Great  was  his  surprise  when  two  years  after- 
wards he  found  that  the  planet  had  become  round  again. 
We  now  know  that  these  appearances  are  due  to  the 
periodical  vanishings  of  the  rings,  owing  to  the  fact  that 
as  Saturn  moves  onward  in  its  orbit,  we  sometimes  behold 

116 


SATURN,   THE   RINGED   WORLD 

the  ring  system,  which  is  very  thin,  directly  in  the  line  of 
vision,  and  thus  see  it  edgewise.  Galileo  knew  nothing  of 
this,  and  he  was  astonished  at  the  planet's  change  of  shape. 
He  was  utterly  cast  down.  Writing  to  his  friend  the 
ambassador  of  the  Grand  Duke  of  Tuscany,  in  the  end  of 
1612,  he  said  :  "Were  the  appearances  indeed  illusion  or 
fraud,  with  which  the  glasses  have  so  long  deceived  me  as 
well  as  many  others  to  whom  I  have  shown  them  ?  I  do 
not  know  what  to  say  in  a  case  so  surprising,  so  unlooked 
for  and  so  novel.  The  shortness  of  the  time,  the  unex- 
pected nature  of  the  event,  the  weakness  of  my  under- 
standing, and  the  fear  of  being  mistaken  have  greatly 
confounded  me."  So  much  was  Galileo  disappointed  at 
his  failure  to  solve  the  problem,  that  he  gave  up  observing 
Saturn  altogether.  It  was  left  to  a  later  astronomer,  the 
Dutchman  Huyghens,  to  demonstrate  the  true  nature  of 
the  appearances.  With  the  aid  of  telescopes  much  more 
powerful  than  those  used  by  Galileo,  he  came  to  the  con- 
clusion that  the  planet  was  surrounded  by  a  ring.  But 
he  was  not  absolutely  certain,  and  he  wished  to  test  his 
theory  so  that  there  would  be  no  possibility  of  mistake. 
In  those  days  it  was  the  custom  of  men  of  science  to 
publish  their  discoveries  to  the  world  in  the  form  of 
anagrams.  That  is  to  say,  they  wished  to  secure  for  them- 
selves the  right  of  discovery  and  at  the  same  time  have 
the  opportunity  of  confirming  their  theories.  Accordingly 
he  jotted  down  a  number  of  letters  in  chaotic  form, 
and  published  them  in  an  apparently  senseless  jumble. 
Huyghens  was  afraid  that  while  testing  his  theory  of  the 
existence  of  a  ring  some  other  astronomers  might  make  the 
discovery  independently,  and  thus  rob  him  of  the  honour. 
Therefore  he  published  the  following  anagram  in  1656  — 

"aaaaaaa,     c  c  c  c  c,     d,     e  e  e  e  e,     g,     h,     i  i  i  i  i  i  i,     1111, 
mm,   nnnnnnnun,   oooo,   pp,   q,   r  r,   s,   tttt,   uuuuu." 

117 


SATURN,   THE   RINGED   WORLD 

Three  years  later  he  arranged  the  letters  in  their  natural 
order,  having  satisfied  himself  that  his  theory  was  correct. 
This  made  up  the  following  Latin  sentence — "Annulo 
cingitur  tenui  piano  nusquam  cohaerante  ad  eclipticum 
inclinato."  Translated  into  English  this  reads — "The 
planet  is  surrounded  by  a  slender  flat  ring  inclined  to  the 
ecliptic  and  nowhere  touching  the  body  of  the  planet." 
Many  years  afterwards  it  was  found  that  the  ring  was 
really  composed  of  two  rings.  We  now  know  of  the 
existence  of  three  ;  within  the  two  bright  rings  there  is  a 
third  known  as  the  dusky  ring.  It  was  the  last  of  the 
three  to  be  discovered,  and  was  first  detected  in  1850. 

For  many  years  it  was  supposed  that  the  ring  system 
was  a  solid  whole — that  the  rings  were  flat  planes.  But 
it  has  been  now  proved  that  they  are  not  solid,  being 
made  of  innumerable  small  satellites  or  rather  meteorites, 
and  so  close  together  are  these  minute  bodies  that  they 
appear  from  this  vast  distance  as  a  complete  solid.  They 
are  in  constant  revolution  round  the  planet.  From  Saturn 
it  is  probable  that  they  appear  as  a  continuous  whole. 
Indeed,  from  the  surface  of  the  planet  the  ring-system 
must  seem  both  magnificent  and  stupendous. 

Let  us  imagine  ourselves  on  the  globe  of  Saturn  on  a 
journey  from  the  pole  to  the  equator,  keeping  a  close 
watch  on  the  Satumian  heavens.  From  the  poles  the 
rings  are  invisible.  As  we  move  equatorwards,  the  system 
gradually  comes  into  view.  As  we  advance,  the  rings  rise 
higher  and  higher  above  the  horizon.  At  the  same  time 
they  diminish  in  breadth  as  we  see  them  more  and  more 
foreshortened.  At  the  equator  they  are  exactly  overhead, 
and  we  only  see  the  interior  edge  of  the  system  as  a 
narrow  arch  extending  right  round  the  heavens.  From 
a  latitude  of  twenty-eight  degrees  on  Saturn,  says  the 

118 


SATURN,   THE   RINGED   WORLD 

French  writer  Guillemin,  "  the  ring-system  is  seen  as  an 
immense  arch,  interrupted  by  a  large  space  at  the  summit. 
The  sky  is  visible  through  the  division  which  separates 
the  two  principal  rings,  and  it  again  appears  below  the 
arch.  The  interruption  at  the  summit  is  produced  by 
the  shadow  cast  by  Saturn,  and  it  is  only  distinguished 
from  the  sky  by  the  absence  of  stars.  It  is  possible, 
however,  that  this  eclipsed  portion  of  the  rings  may  be 
sometimes  rendered  visible  by  the  refraction  of  the  solar 
rays  by  the  atmosphere  of  the  planet.  .  .  .  When  we 
add  to  the  strange  beauty  of  the  spectacle  the  presence 
of  the  satellites  presenting  different  phases,  some  full, 
others  new,  others  gibbous  or  crescent,  an  idea  will  be 
formed  of  the  variety  of  aspect  of  the  Saturnian  nights." 

This  description  applies  only  to  the  summer  time  of 
the  particular  hemisphere  of  the  planet  for  which  it  is 
intended.  In  winter  the  ring-system  reflects  no  light 
whatever  to  the  planet.  Not  only  do  the  rings  give  no 
light  during  the  Saturnian  winter,  but  they  cut  off  the 
light  of  the  Sun  from  the  planet.  They  totally  eclipse 
the  Sun  for  long  periods  at  a  time.  For  fifteen  years, 
half  of  the  period  of  Saturn's  revolution,  the  Sun  is  to  the 
south  of  the  rings,  and  for  fifteen  years  to  the  north,  but 
the  shadow  of  the  ring-system  is  so  broad  that  the  regions 
midway  between  pole  and  equator  on  Saturn  have  to 
suffer  eclipses  which  last  for  more  than  five  of  our  years 
at  a  time.  Saturn  is  at  a  much  greater  distance  from  the 
Sun  than  the  Earth,  and  receives  much  less  sunlight ;  con- 
sequently it  can  ill  afford  to  be  deprived  for  long  periods 
at  a  time  of  the  little  sunshine  which  is  its  due.  Saturn 
therefore  does  not  seem  a  very  inviting  dwelling-place  for 
human  beings. 

In  all  probability,  however,  there  are  no  inhabitants  on 

119 


SATURN,   THE   RINGED   WORLD 

the  planet.  We  learn  this  from  a  study  of  the  globe 
itself.  Saturn  is  the  second  largest  planet  in  the  solar 
system,  and  has  a  diameter  of  74,000  miles.  Suppose  we 
represent  the  Earth  by  a  pea ;  in  proportion  we  may  take 
an  orange  to  represent  Saturn.  Its  distance  from  the  Sun 
is  nearly  nine  hundred  millions  of  miles,  and  it  requires 
almost  thirty  years  to  revolve  once  round  the  central 
luminary.  Like  the  Earth,  Saturn  rotates  on  its  axis. 
This  rotation  is  performed  in  Saturn's  case  in  10  hours 
16  minutes — a  much  more  rapid  rate  of  rotation  than 
that  of  our  world,  notwithstanding  the  greater  size  of  the 
ringed  planet. 

The  globe  of  Saturn,  apart  from  the  rings,  is  a  striking 
spectacle — although  not  so  striking  as  Jupiter — seen 
through  a  good  telescope.  The  cloud  belts  do  not  show 
the  same  rapidity  of  change  as  do  those  of  Jupiter.  Still, 
changes  are  apparent  to  the  careful  observer.  The  only 
surface  of  Saturn  which  we  can  see  is  its  atmosphere, 
which  is  so  dense  and  cloud-laden  that  beyond  it  nothing 
is  visible.  On  the  Earth,  and  also  on  Mars  and  Venus, 
the  atmospheric  clouds  are  raised  by  the  heat  of  the  Sun. 
Venus,  for  instance,  has  a  denser  atmosphere  than  our 
world,  probably  because  it  is  closer  to  the  Sun.  Mars,  on 
the  other  hand,  has  a  thinner  atmosphere.  But  Saturn 
is  at  a  much  greater  distance,  and  at  that  distance  the 
heat  of  the  Sun  is  so  diminished  in  power  that  it  could 
not  be  responsible  for  the  existence  of  an  atmosphere  so 
much  more  cloud-laden  than  ours.  The  heat  which  raises 
the  clouds  comes  not  from  the  Sun,  but  from  the  planet 
itself.  Like  Jupiter,  Saturn  appears  to  be  in  a  much 
earlier  stage  of  development  than  the  Earth.  The  oceans 
which  will  at  some  future  date  settle  down  on  the  planet's 
surface  exist  at  present  only  in  the  form  of  masses 

120 


SATURN,  THE   RINGED   WORLD 

of  cloud  floating  in  the  atmosphere.  It  is  more  than 
doubtful  whether  Saturn  has  any  solid  surface  beneath  the 
dense  canopy  of  clouds.  It  may  have  a  crust  partly 
solidified,  but  subject  to  violent  eruptions,  such  as  seem  to 
have  been  prevalent  during  the  early  stages  of  the  life  of 
our  own  world.  Let  us  picture  to  ourselves  what  goes  on 
beneath  those  cloud  belts.  A  world  in  a  state  of  chaos 
exists  there — violent  eruptions  take  place ;  boiling,  seething 
masses  of  fire  shoot  through  the  partly  solidified  crust. 
It  is  a  world  of  restless  turmoil  and  sweltering  heat. 
This  view  of  the  condition  of  Saturn  is  confirmed  by  the 
fact  that  while  it  is  about  seven  hundred  times  larger 
than  the  Earth,  it  is  only  ninety  times  as  heavy.  Indeed, 
in  proportion  to  its  size,  Saturn  is  the  lightest  of  all  the 
planets.  It  is  only  equal  in  weight  to  a  globe  of  walnut 
wood  of  the  same  size.  In  fact,  if  we  could  imagine 
a  great  ocean  large  enough  to  hold  the  various  planets, 
and  if  we  could  imagine  the  planets  thrown  one  by  one 
into  that  ocean,  Saturn  would  actually  float  while  all  the 
others  would  sink.  The  extraordinary  lightness  of  Saturn 
is  explained  by  its  condition  of  intense  heat. 

Thus  we  see  that  in  two  particulars  Saturn  is  unique  in 
the  solar  system.  It  is  the  lightest  of  all  the  planets, 
and  it  possesses  a  marvellous  system  of  rings.  But  in 
another  respect  it  is  also  unique.  So  far  as  we  know, 
it  possesses  more  satellites  than  any  other  planet.  There 
are  no  fewer  than  ten  of  these  little  bodies  owning  it 
allegiance  and  circling  round  it  in  ceaseless  revolution. 
In  order  of  distance  from  the  planet,  the  names  of  these 
little  worlds  are  Mimas,  Enceladus,  Tethys,  Dione,  Rhea, 
Titan,  Hyperion,  Themis,  Japetus,  and  Phoebe.  Of 
these,  Titan  is  by  far  the  largest.  It  was  the  earliest 
discovered,  and  was  first  seen  by  Huyghens  during  his 

121 


SATURN,   THE   RINGED    WORLD 

study  of  the  planet.  It  is  about  three  thousand  miles  in 
diameter,  and  equal  in  size  to  the  planet  Mercury.  Indeed 
Titan  is  quite  a  little  world  in  itself.  The  faintest,  and 
probably  the  smallest,  is  Themis,  which  was  discovered  in 
1905  by  Professor  W.  H.  Pickering  of  Harvard,  by  means 
of  photography.  So  faint  is  the  little  moon  that  it  is 
quite  invisible  by  ordinary  telescopic  methods,  and  is  only 
known  by  its  image  on  the  photographic  plate. 

The  most  remarkable  member  of  the  system  of  Saturn, 
however,  is  the  little  moon  known  as  Phoebe,  the  most 
distant  of  the  satellites.  All  the  other  nine  moons  revolve 
from  west  to  east,  the  rings  also  revolve  in  that  direction, 
the  planet  likewise  rotates  in  that  direction.  But  Phoebe 
revolves  in  the  opposite  direction — from  east  to  west.  Just 
imagine,  if  we  had  a  number  of  moons  and  one  of  them 
revolved  in  the  opposite  direction  from  the  others,  how  com- 
plicated and  bewildering  our  evening  skies  would  become. 

The  satellites  have  great  diversities  in  their  periods  of 
revolution.  Little  Mimas,  the  closest  to  Saturn  of  the 
ten,  is  at  a  distance  of  115,000  miles,  and  revolves  in 
22  hours  37  minutes.  Phoebe  requires  sixteen  months 
for  its  slow  revolution  round  its  primary.  In  the  heavens 
Saturn,  with  its  magnificent  system  of  rings  and  its 
gorgeous  retinue  of  moons,  is  a  spectacle  as  majestic  as 
it  is  unique.  If  any  of  its  satellites  be  inhabited,  these 
inhabitants  will  probably  regard  the  planet  as  we  regard 
the  Sun — as  light  giver  and  heat  giver ;  and  with  good 
reason  will  they  look  on  Saturn  as  their  Sun,  as  probably 
it  gives  out  a  certain  amount  of  intense  heat.  Supposing 
either  Saturn  or  its  satellites  were  inhabited,  the  in- 
habitants would  be  hardly  able  to  catch  a  glimpse  of  our 
Earth.  Seen  from  Saturn,  the  Earth  is  a  small  insignificant 
point,  lost  in  the  light  of  the  far-away  luminary,  the  Sun. 


CHAPTER   XII 
THE   BOUNDARIES   OF   THE   SOLAR   SYSTEM 

SATURN  was  the  most  distant  world  known  to  the 
ancients.  They  regarded  its  orbit  as  the  boundary 
of  the  planetary  system,  and  it  was  not  until  the 
year  1781  that  astronomers  learned  that  the  solar  system 
extended  to  a  much  greater  distance  than  the  orbit  of 
Saturn.  Of  the  two  distant  planets  Uranus  and  Neptune 
little  is  known,  but  the  story  of  their  discovery  is  one  of 
the  most  interesting  chapters  in  the  history  of  astronomy. 
To  the  genius  and  skill  of  William  Herschel  we  owe 
the  discovery  of  the  planet  Uranus.  The  record  of  this 
discovery  is  so  bound  up  with  the  life-story  of  the 
discoverer  that  it  is  impossible  to  separate  them.  That 
life-story 1  is  a  record  of  endless  perseverance,  boundless 
energy,  and  undying  enthusiasm.  The  most  striking  of  all 
discoveries,  however,  was  nothing  less  than  that  of  a  new 
planet  revolving  beyond  the  orbit  of  Saturn — the  first 
new  member  of  the  solar  system  discovered  within  the 
memory  of  man.  On  March  13,  1781,  while  observing 
the  stars  in  the  constellation  Gemini,  he,  in  his  own 
words,  "  perceived  one  that  appeared  visibly  larger  than 
the  rest."  Comparing  it  with  other  stars  in  the  vicinity, 
and  "  finding  it  to  be  so  much  larger  than  either  of  them, 
he  suspected  it  to  be  a  comet."  For  some  time  it  was 
believed  to  be  one  of  these  objects,  but  when  its  orbit  had 

1  See  the  chapter  on  the  "  Conquest  of  the  Stars ." 
123 


BOUNDARIES   OF   SOLAR  SYSTEM 

been  calculated  by  mathematical  astronomers  it  soon 
became  apparent  that,  instead  of  revolving  in  a  very  long 
ellipse  as  most  comets  do,  it  moved  in  an  orbit  almost 
circular.  There  was  no  doubt  therefore  that  the  German 
musician  had  discovered  not  a  comet,  but  a  new  planet, 
and  had  doubled  by  this  discovery  the  diameter  of  the 
solar  system. 

The  scientific  world  was  amazed  at  the  discovery.  It 
had  never  even  suspected  that  an  unknown  orb  revolved 
beyond  the  orbit  of  Saturn.  It  was,  however,  even  more 
surprising  to  find  that  Uranus  had  often  been  seen  and 
catalogued  as  an  ordinary  star — no  fewer,  indeed,  than 
seventeen  times.  Flamsteed,  the  first  Astronomer  Royal 
of  England,  observed  Uranus  four  times  in  different 
positions,  and  did  not  notice  the  difference  of  place.  A 
French  astronomer,  Le  Monnier,  narrowly  escaped  dis- 
covering the  planet  in  1769,  and  would  certainly  have 
done  so  but  for  the  careless  and  slovenly  way  in  which 
he  jotted  down  his  observations. 

Herschel  proposed  to  name  the  new  planet  "  Georgian! 
Sidus  "  (the  Star  of  George),  after  his  patron  George  the 
Third.  This  title  naturally  found  no  favour  on  the 
Continent.  A  French  astronomer  suggested  the  name 
Herschel  after  the  discoverer  himself,  while  Bode  of 
Berlin  suggested  Uranus,  in  keeping  with  the  custom  of 
naming  the  planets  after  the  Greek  and  Roman  divinities. 
All  these  names  were  in  use  for  a  considerable  time,  but  at 
length  the  name  Uranus  prevailed,  and  is  now  universally 
adopted. 

The  discovery  of  Uranus  was  a  remarkable  achieve- 
ment, but  it  led  to  one  still  more  remarkable — the 
detection  of  a  planet  still  farther  removed  from  the 
Sun.  After  Uranus  had  been  duly  recognised  as  a  member 


BOUNDARIES   OF    SOLAR  SYSTEM 

of  the  Sun's  family  of  planets,  its  orbit  was  calculated. 
In  making  these  calculations  astronomers  utilised  the 
early  observations  of  Uranus  made  by  the  observers 
who  had  failed  to  notice  its  difference  from  an  ordi- 
nary star.  The  observations  were  far  from  useless,  for 
although  these  observers  had  failed  to  make  the  discovery 
which  was  within  their  grasp,  they  had  measured  care- 
fully the  positions  of  their  supposed  star.  This  was  all 
that  mathematicians  needed  to  enable  them  to  calculate 
the  planet's  orbit  with  a  further  approach  to  accuracy. 
Bouvard,  a  French  astronomer,  published  tables  giving 
the  planet's  positions  in  the  future.  But  as  Uranus  did 
not  conform  to  the  orbit  which  had  been  laid  down  for  it, 
Bouvard  concluded  that  there  must  be  some  mistake  in 
the  earlier  observations.  Accordingly  in  1821  he  rejected 
these  altogether,  and  published  a  new  series  of  tables, 
utilising  only  the  observations  made  since  Herschel's  time. 
Again,  however,  the  planet  was  not  in  the  predicted 
place.  The  error  was  very  minute,  it  is  true  ;  as  the  late 
Miss  Clerke  points  out,  "  if  the  theoretical  and  the  real 
Uranus  had  been  placed  side  by  side  in  the  sky,  they 
would  have  seemed  to  the  sharpest  eye  to  form  a  single 
body."  In  an  exact  science  like  astronomy,  however,  an 
error  like  this  is  intolerable,  and  is  evidence  of  some  flaw 
in  the  theory.  Some  astronomers  began  to  doubt  the 
universality  of  the  law  of  gravitation  on  which  all  these 
calculations  were  founded,  and  to  ask  if  the  law  did  not 
break  down  at  the  boundaries  of  the  solar  system. 

Gradually  the  idea  dawned  on  astronomers  that  perhaps 
another  planet,  at  a  greater  distance  from  the  Sun,  was 
attracting  Uranus  from  the  predicted  path.  The  problem 
was,  how  could  this  be  tested.  It  is  no  easy  matter  to 
search  through  thousands  of  stars  along  the  zodiacal 


BOUNDARIES  OF   SOLAR  SYSTEM 

constellations  to  find  a  planet :  such  a  task  would  be 
impossible.  The  only  hope  of  detecting  the  planet  lay 
in  calculating  its  position  from  its  influence  on  Uranus. 
Here  was  a  mighty  problem  involving  great  mathematical 
powers.  One  of  the  greatest  calculators  of  the  day  re- 
solved to  grapple  with  the  question,  but  he  died  before 
the  discovery  was  made.  Another  astronomer  intended 
to  investigate  the  matter,  but  found  it  beyond  his  powers. 
At  length  two  investigators  in  England  and  France 
respectively  took  up  the  question  independently  and 
quite  unknown  to  each  other.  Adams,  a  student  at  the 
University  of  Cambridge,  noted  in  his  diary  in  1841  his 
resolve  to  investigate  "  the  irregularities  in  the  motions 
of  Uranus,  which  are  as  yet  unaccounted  for,  in  order  to 
find  whether  they  may  be  attributed  to  the  action  of  an 
undiscovered  planet  beyond  it ;  and,  if  possible,  thence  to 
determine  the  elements  of  its  orbit  approximately,  which 
would  lead  probably  to  its  discovery/1  In  1843,  after 
taking  his  degree  at  Cambridge,  he  commenced  his  in- 
vestigation, which  occupied  him  for  two  years.  On 
October  21,  1845,  he  called  at  Greenwich  Observatory, 
and  left  a  paper  containing  the  elements,  position,  orbit, 
&c.,  of  the  supposed  planet,  and  approximately  fixing  its 
position  in  the  heavens — expecting  that  the  Astronomer 
Royal  of  England,  Sir  George  Airy,  would  institute  a 
search  for  the  body.  Airy,  however,  was  not  particularly 
interested  in  this  question  ;  he  was  above  all  what  may  be 
called  a  practical  astronomer,  and  he  paid  little  attention 
to  the  paper  which  the  young  Cambridge  graduate  left  for 
his  consideration.  Adams,  too,  did  not  seem  particularly 
anxious  to  have  a  search  instituted,  and  the  result  was  that 
his  paper  remained  in  obscurity  until  it  was  too  late.  In 
1 845,  Le  Verrier,  one  of  the  rising  astronomers  of  France, 

126 


BOUNDARIES   OF   SOLAR   SYSTEM 

also  undertook  to  solve  the  problem,  and  he  also  assigned 
the  position  in  the  heavens  of  the  disturbing  planet  in 
the  constellation  Aquarius.  Sir  George  Airy  happened 
to  see  one  of  the  papers  in  which  Le  Verrier  had  pub- 
lished his  conclusions.  He  was  impressed  by  the  fact 
that  the  two  independent  investigators  had  reached  the 
same  result,  and  accordingly  he  wrote  to  the  director  of 
the  Observatory  at  Cambridge  requesting  him  to  search 
the  region  of  the  heavens  to  which  Adams'1  calculations 
pointed.  The  Cambridge  astronomer  commenced  a  search, 
but  he  had  no  star-maps,  and  had  to  chart  the  region 
of  the  heavens  before  he  could  search  for  the  planet.  At 
length  Le  Verrier,  having  completed  his  investigations, 
wrote  to  Encke,  director  of  the  Berlin  Observatory, 
requesting  him  to  search  for  the  planet.  Encke  at  once 
set  two  of  his  assistants,  D"1  Arrest  and  Galle,  on  the 
search,  with  the  result  that  in  a  few  hours,  by  the  aid  of 
some  recently  published  star-maps,  Galle  perceived,  almost 
exactly  in  the  position  indicated  by  Le  Verrier,  a  strange 
star,  which  was  soon  identified  as  the  disturber  of  the 
motions  of  Uranus. 

Thus  was  the  great  discovery  accomplished,  and  another 
planet  added  to  the  solar  system.  The  name  of  the 
newly  found  celestial  object  was  more  easily  settled  than 
that  of  HerschePs  planet.  The  following  extract  from 
the  reminiscences  of  Sir  Henry  Holland,  the  well-known 
physician,  tells  us  of  the  naming  of  this  distant  world. 
After  referring  to  his  visits  to  foreign  Observatories, 
undertaken  owing  to  his  great  interest  in  astronomy,  he 
says :  "  That  which  most  strongly  clings  to  my  memory 
is  an  evening  I  passed  with  Encke  and  Galle  in  the 
Observatory  of  Berlin,  some  ten  or  twelve  days  after  the 
discovery  of  the  planet  on  this  very  spot ;  and  when 

127 


BOUNDARIES   OF   SOLAR  SYSTEM 

every  night's  observations  of  its  motions  had  still  an 
especial  value  in  denoting  the  elements  of  its  orbit.  I 
had  casually  heard  of  the  discovery  at  Bremen,  and  lost 
no  time  in  hurrying  on  to  Berlin.  The  night  in  question 
was  one  of  floating  clouds,  gradually  growing  into  cumuli, 
and  hour  after  hour  passed  away  without  sight  of  the 
planet  which  had  just  come  to  our  knowledge  by  so 
wonderful  a  method  of  predictive  research.  Frustrated 
in  this  main  point,  it  was  some  consolation  to  stay  and 
converse  with  Encke  in  his  own  Observatory,  one  signalised 
by  so  many  discoveries,  the  stillness  and  darkness  of  the 
place  broken  only  by  the  ticking  of  the  astronomical 
clock,  which  as  the  unfailing  interpreter  of  the  celestial 
times  and  motions,  has  a  sort  of  living  existence  to  the 
astronomer.  Among  other  things  discussed  while  thus 
sitting  together  in  a  sort  of  tremulous  impatience  was 
the  name  to  be  given  to  the  new  planet.  Encke  told  me 
he  had  thought  of  Vulcan,  but  deemed  it  right  to  remit 
the  choice  to  Le  Verrier,  then  supposed  the  sole  indicator 
of  the  planet  and  its  place  in  the  heavens,  adding  that 
he  expected  Le  Verrier*s  answer  by  the  first  post.  Not 
an  hour  had  elapsed  before  a  knock  at  the  door  of  the 
Observatory  announced  the  letter  expected.  Encke  read 
it  aloud,  and,  coming  to  the  passage  where  Le  Verrier 
proposed  the  name  of  '  Neptune,"*  exclaimed  *  So  lass  den 
namen  Neptun  sein?  It  was  a  midnight  scene  not  easily 
to  be  forgotten.  A  royal  baptism,  with  its  long  array 
of  titles,  would  ill  compare  with  this  simple  naming  of  the 
remote  and  solitary  planet  thus  wonderfully  discovered." 

Thus  closes  the  record  of  a  remarkable  discovery — 
perhaps  the  most  remarkable  ever  made  in  astronomy, 
The  discovery  of  Neptune  was  not  only  a  magnificent 
attack  on  the  secrets  of  Nature,  but  a  glorious  triumph 

128 


BOUNDARIES   OF   SOLAR  SYSTEM 

of  the  human  intellect.  The  honour  of  the  discovery  is 
now  given  equally  to  Adams  and  Le  Verrier,  although 
for  some  time  controversy  raged  as  to  which  of  the  two 
deserved  most  glory.  If  Le  Verrier's  results  were  slightly 
more  accurate  than  those  of  Adams,  the  latter  investigator 
was  earlier  with  his  calculations.  In  this  chapter  much 
space  has  been  given  to  the  history  of  these  two  discoveries. 
In  the  case  of  the  well-known  planets,  we  know  nothing 
of  their  discovery,  but  we  have  bonsiderable  knowledge 
of  their  physical  condition.  In  the  case  of  the  distant 
worlds  we  know  practically  nothing  of  their  physical  con- 
dition, while  the  story  of  the  two  discoveries,  the  second 
the  outcome  of  the  first,  forms  one  of  the  most  fascinating 
chapters  in  the  history  of  science. 

Dusky  bands,  resembling  those  of  Jupiter,  were  noticed 
on  the  disc  of  Uranus  in  1883  by  the  late  Professor 
Young.  Some  astronomers  consider  that  the  planet 
rotates  on  its  axis  in  about  ten  hours,  but  this  has  not 
been  confirmed  by  other  observers.  However,  various 
facts  tend  to  show  that  its  period  of  rotation  must  be 
short.  Uranus,  so  far  as  is  known,  is  in  a  condition 
of  great  heat.  The  spectroscope  has  shown  that  free 
hydrogen  exists  in  the  Uranian  atmosphere,  and  this 
indicates  the  existence  of  a  temperature  high  enough  to 
separate  water  into  its  constituent  elements.  Observa- 
tions at  the  Lowell  Observatory  a  few  years  ago  indicated 
the  existence  in  the  planet's  atmosphere  of  the  element 
helium. 

Uranus  has  four  satellites,  known  as  Ariel,  Umbriel, 
Titania,  and  Oberon.  Of  these  the  two  last  named  were 
discovered  by  Sir  William  Herschel  in  1787.  Ariel  was 
glimpsed  by  the  astronomer  Lassell  on  14th  September 
1847,  and  Umbriel  by  Otto  Struve  a  few  weeks  later, 

129  I 


BOUNDARIES   OF   SOLAR   SYSTEM 

their  existence  being  finally  confirmed  by  Lassell's  obser- 
vations a  few  years  later.  The  satellites  are  very  faint. 
Ariel,  the  nearest  satellite,  revolves  round  Uranus  in 
2  days  12  hours,  at  a  mean  distance  of  124,000  miles. 
Umbriel  revolves  in  4  days  3  hours,  at  a  mean  distance 
of  173,000  miles.  Titania,  at  a  mean  distance  of  285,000 
miles,  revolves  in  8  days  1 6  hours ;  while  Oberon,  at  a 
mean  distance  of  381,000  miles,  requires  13  days  11  hours 
to  circle  round  its  primary.  Nothing  is  known  of  the 
physical  condition  of  these  satellites.  A  remarkable  fact 
connected  with  them  is  that  they  revolve  almost  at  right 
angles  to  the  plane  of  the  ecliptic,  in  which  most  of  the 
planets  and  satellites  move.  It  is  quite  possible  that  there 
may  be  other  satellites  of  Uranus  yet  undiscovered. 

If  little  is  known  of  Uranus,  less  is  known  of  Neptune  ; 
the  two  worlds  are  about  the  same  size,  and  seem  to  have 
many  points  in  common.  The  spectrum  of  Neptune  has 
been  investigated  by  various  observers,  who  have  found  it 
to  resemble  closely  that  of  Uranus.  In  1883,  Mr.  Maxwell 
Hall,  an  astronomer  in  Jamaica,  noticed  certain  variations 
of  brightness,  which  he  believed  indicated  that  the  planet 
rotated  on  its  axis  in  about  8  hours,  but  this  observa- 
tion has  not  been  confirmed.  Neptune  has  one  satellite, 
so  far  as  is  known.  It  was  discovered  by  Lassell  on 
10th  October  1846— only  a  fortnight  after  the  planet 
itself  was  detected.  It  is  situated  at  a  distance  of  223,000 
miles  from  its  primary,  round  which  it  moves  in  5  days 
21  hours  8  minutes.  Like  the  Uranian  moons,  its  motion 
is  retrograde.  It  must  be  very  large  to  be  visible  at  all 
at  a  distance  so  vast.  Some  astronomers  consider  that  it 
is  the  largest  satellite  in  the  solar  system.  Probably  it 
is  over  three  thousand  miles  in  diameter. 

We  have  now  described  the  outermost  planet  of  the 

130 


BOUNDARIES   OF  SOLAR   SYSTEM 

solar  system,  revolving  in  solitary  loneliness.  But  is  the 
orbit  of  Neptune  really  the  frontier  of  the  Sun's  domain  ? 
Are  there  planets  beyond  Neptune  ?  Astronomical 
science  has  not  yet  answered  these  questions.  The 
existence  of  one  planet  at  least  has  been  strongly  sus- 
pected, and  at  the  present  time  (1910),  Professor  W.  H. 
Pickering  is  undertaking  a  search  for  a  world  beyond 
Neptune,  the  existence  of  which  he  believes  to  be  indi- 
cated by  its  influence  on  the  motion  of  certain  comets. 
It  may,  however,  be  many  years  before  such  a  planet,  if 
it  exists,  is  detected. 

We  have  now  come  to  the  end  of  a  description  of  the 
solar  system,  proceeding  outwards  from  the  Sun.  But 
the  planets  and  their  satellites  are  not  the  only  bodies  in 
the  solar  system.  There  exists  another  class  of  celestial 
objects — the  cometary  and  meteoric  bodies.  To  the 
consideration  of  these  the  next  few  chapters  will  be 
devoted. 


131 


CHAPTER   XIII 
THE   SUN'S   FAMILY   OF   COMETS 

OF  all  the  celestial  bodies,  perhaps  comets  are  the 
most  remarkable  and  the  most  mysterious.     They 
are  totally  unlike  the  planets ;  instead  of  being 
round    solid   globes,   they   seem    to    be    diffused    masses. 
Instead    of    revolving    round    the    sun    in    orbits    nearly 
circular,  those  comets  which  have  been  proved  to  belong 
to  the  solar  system  move  in  enormously  long  ellipses,  and 
are  only  seen  for  a  brief  period  when  in  the  vicinity  of 
the  Sun  and  the  Earth. 

Among  the  ancients,  and  indeed  in  the  Middle  Ages, 
comets  were  a  source  of  terror  to  mankind,  and  were 
regarded  as  terrible  portents  of  wars,  famines,  deaths  of 
kings,  and  other  national  calamities.  A  bright  comet 
which  appeared  in  1066  was  supposed  to  be  a  portent 
of  the  Norman  Conquest  of  England.  Another  which 
was  seen  in  1456  was  believed  to  be  connected  with  the 
taking  of  Constantinople  by  the  Turks.  In  the  Middle 
Ages,  it  has  been  remarked,  every  comet  "  was  believed  to 
be  a  ball  of  fire  flung  from  the  right  hand  of  an  angry 
God,"  and  this  view  was  by  no  means  confined  to  the 
ignorant.  We  find  Martin  Luther  and  John  Knox  firmly 
believing  in  the  direful  effects  of  comets  on  the  Earth  and 
its  inhabitants.  In  the  seventeenth  century  an  illness 
among  cats  in  Germany  was  actually  ascribed  to  the 
appearance  of  a  comet.  In  our  time,  thanks  to  the 
advance  of  science,  we  know  that  comets  have  no  effect 


THE   SUN'S  FAMILY  OF   COMETS 

whatever  on  the  Earth,  either  baneful  or  beneficial. 
Consequently  terror  at  brilliant  comets  has  given  way 
to  wonder  and  admiration. 

A  bright  comet  may  be  said  to  consist  of  three  parts — 
coma,  nucleus,  and  tail — while  faint  comets  only  seen  in 
telescopes  generally  lack  the  tail.  To  the  ordinary  star- 
gazer  a  comet  is  an  object  with  a  tail ;  but,  as  a  matter 
of  fact,  comets  with  tails  are  far  outnumbered  by  comets 
without  tails — little  comets  which  are  only  seen  with  the 
aid  of  the  telescope,  and  which  were  consequently  un- 
known to  the  ancient  astronomers.  Some  comets  not  only 
lack  a  tail,  but  are  also  wanting  in  coma  and  appear  like 
round  diffused  planetary  discs.  As  was  seen  in  previous 
chapters,  the  planet  Uranus  was  at  first  believed  by 
Herschel  to  be  a  telescopic  comet,  and  Ceres,  the  first 
discovered  of  the  asteroids,  was  also  taken  for  a  comet. 
When  a  comet  is  first  seen  in  a  powerful  telescope,  or 
first  imprints  its  image  on  a  photographic  plate,  it  is 
merely  a  round  faint  nebulosity.  As  it  approaches  the 
Sun,  if  it  is  going  to  be  a  prominent  comet,  it  develops 
the  well-known  tail  or  tails,  for  comets  have  been  known 
with  two,  three,  and  as  many  as  six  tails. 

Comets  are  of  two  kinds — those  which  belong  to  the 
solar  system,  and  those  which  do  not,  and  in  this  chapter 
attention  is  given  to  the  former  class.  The  scientific 
study  of  comets  only  began  about  the  year  1680,  when 
Sir  Isaac  Newton,  in  his  investigation  of  them,  demon- 
strated that  they  were,  like  the  planetary  bodies,  subject 
to  the  action  of  the  law  of  gravitation.  Newton  himself 
did  not  prove  that  any  particular  comet  revolved  round 
the  Sun.  This  was  reserved  for  his  friend  Halley,  who 
in  1705  stated  his  conclusions  on  the  subject. 

Of  all  the  comets  which  have  been  seen  by  the 

133 


THE  SUN'S  FAMILY  OF  COMETS 

Earth's  inhabitants,  the  most  famous  is  that  which  bears 
Halley 's  name.  It  was  not  the  brightest  seen,  nor  the 
most  remarkable ;  but  it  was  the  first  which  was  de- 
finitely proved  to  revolve  round  the  Sun.  There  have  been 
brighter  comets,  such  as  Donatf  s,  and  the  great  comet 
of  1811  ;  but  the  chief  interest  in  Halley 's  Comet  lies  in 
its  regular  returns  at  intervals  of  seventy-three  or  seventy- 
four  years. 

In  the  year  1682,  while  Newton  was  busily  engaged  in 
testing  his  law  of  gravitation,  a  bright  comet  made  its 
appearance,  and  was  attentively  studied  by  the  foremost 
astronomers  of  the  day.  Among  these  was  Edmund 
Halley,  the  well-known  Englishman,  who  became  the 
second  Astronomer  Royal  of  England.  It  occurred  to 
Halley  that  comets  possibly  revolved  round  the  Sun  in 
orbits  similar  to  those  of  the  planets,  and  that  it  would 
be  useful  to  investigate  as  to  whether  a  comet  had 
been  seen  more  than  once.  As  Sir  Robert  Ball  says : 
"At  the  expense  of  much  labour,  he  laid  down  the 
paths  pursued  by  twenty-four  of  these  bodies  which  had 
appeared  between  1337  and  1698.  Amongst  them  he 
noticed  three  which  followed  tracks  so  closely  resembling 
each  other  that  he  was  led  to  conclude  that  the  so-called 
three  comets  could  only  have  been  three  different  ap- 
pearances of  the  same  body/1  The  first  of  these  three 
comets  had  been  seen  in  1531,  while  the  second  was 
observed  by  Kepler  in  1607,  and  the  third  was  the  bright 
comet  studied  by  Halley  himself  in  1682.  The  astro- 
nomer also  noticed  that  bright  comets  had  been  seen 
in  1456,  seventy-five  years  before  1531,  in  1380,  and 
also  in  1305,  at  intervals  of  about  seventy-six  years. 
After  a  careful  study  of  the  comet's  orbit,  and  of  the 
effect  which  Jupiter  would  have  in  retarding  the  return, 

134 


DONATI'S  COMET,  1858 

This  comet  is  generally  believed  to  have  been  the  finest  cometary  spectacle  of  the 
last  century. 


THE  SUN'S  FAMILY  OF  COMETS 

Halley  predicted  that  the  comet  would  reappear  in  the 
end  of  1758  or  the  beginning  of  1759.  He  knew  that 
he  himself  would  be  dead  long  before  its  return,  and  he 
wrote  thus : — "  If  it  should  return  according  to  our 
predictions,  about  the  year  1758,  impartial  posterity  will 
not  refuse  to  acknowledge  that  this  was  first  discovered 
by  an  Englishman.'*1  Posterity  has  not  refused  to  admit 
this  fact,  and  the  name  of  Halley  has  ever  since  been 
associated  with  the  comet.  The  verification  of  his  pro- 
phecy reflects  a  glory  on  his  name  which  will  cause  it  to 
live  for  ever  among  the  greatest  of  astronomers. 

As  the  year  1758  drew  near,  great  excitement  pre- 
vailed among  men  of  science  to  see  whether  Halley's 
prediction  would  be  fulfilled.  The  astronomer  had  been 
dead  for  sixteen  years,  but  nevertheless  interest  in  his 
prophecy  was  unabated.  The  French  mathematician 
Clairaut,  and  two  other  mathematicians,  undertook  the 
task  of  calculating  the  exact  date  of  the  comet's  return. 
The  outcome  of  these  researches  was  to  show  that  the 
attraction  of  Saturn  would  delay  the  return  of  the  comet 
by  100  days  and  that  of  Jupiter  by  518  days.  Men 
of  science  all  over  the  world  watched  anxiously,  and  at 
last  on  Christmas  Day,  1758,  the  comet  was  sighted  by  an 
amateur,  a  farmer  in  Saxony.  The  comet  reached  its 
perihelion,  or  point  nearest  to  the  Sun,  on  March  12, 1759, 
and  then  disappeared  on  its  long  journey.  In  1835  Hie 
comet  again  reappeared,  and  on  November  15,  1835, 
passed  the  point  of  its  path  closest  to  the  Sun.  Three 
able  mathematical  astronomers  undertook  to  calculate 
the  exact  date  of  the  planet's  perihelion  passage. 
Damoiseau,  a  Frenchman,  fixed  on  November  4,  1835  ; 
Pontecoulant,  another  Frenchman,  fixed  on  November  12  ; 
Rosenberger,  a  German  calculator,  taking  account  of  the 

135 


THE   SUN'S   FAMILY   OF   COMETS 

attractions  of  all  the  principal  planets,  fixed  on  November 
11.  The  perihelion  passage  actually  took  place  on  Novem- 
ber 15 — a  proof  of  the  remarkable  accuracy  of  the  three 
calculators.  In  1835  the  comet  was  first  detected  at 
Rome,  and  was  particularly  studied  by  Sir  John  Herschel, 
who,  on  May  5,  1886,  caught  the  last  glimpse  of  the 
comet  with  his  giant  telescope.  From  1836  to  1873  the 
comet  was  on  its  journey  outward  to  the  most  remote 
point  of  its  orbit,  beyond  the  pathway  of  Neptune.  In 
1873  it  reached  its  aphelion,  as  this  farthest  point  is 
called,  and  then  commenced  returning  with  increasing 
velocity  to  the  regions  of  light  and  heat. 

In  November  1908,  plates  were  exposed  in  the  region 
of  the  heavens  where  it  was  calculated  that  the  comet 
would  appear,  but  it  was  not  until  September  1909  that 
it  was  actually  discovered  photographically  by  Dr.  Max 
Wolf  of  Heidelberg.  The  comet  in  May  1910  was 
disappointing  as  a  spectacular  object  to  observers  in 
Britain ;  but  the  public  interest  was  unprecedented. 
Halley's  was  thus  the  first  comet  which  was  proved  to 
revolve  round  the  Sun  in  an  elliptic  orbit,  and  to  be 
subject  to  the  law  of  gravitation  just  as  the  planets  are. 
Also,  of  all  the  known  periodic  comets,  it  is  the  one 
which  has  the  longest  period  of  revolution. 

The  next  comet  ascertained  to  be  also  periodic,  arid  to 
be  a  member  of  the  Sun's  family,  was  an  insignificant  little 
object  known  as  Encke's  Comet.  On  November  26,  1818, 
Pons,  a  French  astronomer  who  devoted  much  of  his 
attention  to  the  discovery  of  these  objects,  detected  a 
small  telescopic  comet.  The  German  astronomer  Encke 
undertook  to  calculate  the  orbit  of  the  comet,  and  found 
it  to  be  probably  identical  with  comets  discovered  by  the 
French  astronomer  Mechain  in  1786,  by  Caroline  Herschel 

136 


THE   SUN'S   FAMILY   OF   COMETS 

in  1795,  and  by  Thulis  in  1805.  Encke  accordingly  found 
that  the  time  required  for  the  comet  to  revolve  round 
the  Sun  was  three  years  and  a  half,  and  he  calculated 
that  the  comet  would  pass  its  perihelion  point  on  May  24, 
1822.  True  to  Ericke's  prediction,  the  comet  returned, 
and  the  perihelion  passage  took  place  within  three  hours 
of  the  time  which  he  predicted.  As  the  late  Miss  Clerke 
has  remarked :  "  The  importance  of  this  event  will  be 
better  understood  when  it  is  remembered  that  it  was  only 
the  second  instance  of  the  recognised  return  of  a  comet ; 
and  that  it,  moreover,  establishes  the  existence  of  a  new 
class  of  bodies  distinguished  as  comets  of  short  period." 

The  comet  returned  again  in  1825,  and  has  returned 
ever  since  at  regular  intervals.  At  its  return  in  1828,  it 
was  actually  visible  to  the  unaided  eye  as  a  star  of  the 
fifth  magnitude.  In  1838  Encke  made  a  remarkable 
discovery  in  connection  with  his  comet.  He  found  that 
it  returned  to  its  perihelion  point  two  and  a  half  hours 
before  the  predicted  time.  He  accordingly  put  forward 
the  theory  that  this  acceleration  of  the  motion  of  the 
comet  was  due  to  the  existence  of  what  he  called  a  "  re- 
sisting medium  "  in  the  vicinity  of  the  Sun,  too  rarefied 
to  retard  the  motions  of  the  planets,  but  quite  dense 
enough  -to  make  the  path  of  the  comet  smaller,  and 
eventually  to  precipitate  it  on  the  Sun.  This  theory 
was  held  for  a  considerable  time,  but  in  1868  the 
acceleration  began  to  decrease,  and  accordingly  the  theory 
was  abandoned.  At  its  return  in  1904,  the  comet  was 
well  observed,  being  comparatively  bright.  In  1908, 
however,  it  was  very  faint,  and  the  only  record  of  its 
return  in  that  year  was  its  image  on  a  photographic 
plate. 

Mr.  G.  F.  Chambers,  in  his  book  "  The  Story  of  the 
137 


THE  SUN'S  FAMILY  OF  COMETS 

Comets,"  gives  the  number  of  known  short-period  comets 
as  thirteen.  The  periods  of  revolution  vary  from  over 
three  years  in  the  case  of  Encke's  Comet  to  over  thirteen 
in  the  case  of  Brorsen's.  It  would  require  considerable 
space  to  describe  each  of  these  objects  individually.  Only 
some  of  the  more  prominent  can  be  mentioned  here.  In 
1843,  Faye,  at  the  Paris  Observatory,  discovered  a  comet 
which  was  ascertained  to  revolve  round  the  Sun  in  an 
elliptic  orbit  in  over  seven  years.  Its  orbit  is  the  least 
elliptic  of  all  the  short-period  comets.  It  was  last  seen 
at  its  return  in  1895,  being  missed  when  it  reached  its 
perihelion  in  1903.  In  1884,  Dr.  Max  Wolf  discovered, 
at  Heidelberg,  a  telescopic  comet  which  was  proved  to 
revolve  round  the  Sun  in  six  years  and  three-quarters. 
Before  1875,  it  is  doubtful  if  the  comet  was  a  permanent 
member  of  our  system,  as  in  that  year  its  orbit  was 
completely  changed  by  the  great  attractive  power  of 
Jupiter. 

Another  remarkable  comet  was  detected  in  1892  by 
Mr.  Holmes,  an  English  amateur.  Of  this  comet  Pro- 
fessor Barnard,  who  carefully  studied  it  with  the  great 
telescope  of  the  Lick  Observatory,  wrote  as  follows : — 
"From  several  points  of  view  it  was  one  of  the  most 
remarkable  comets  ever  observed.  At  the  time  of  dis- 
covery, it  was  distinctly  visible  to  the  naked  eye  as  a 
slightly  ill-defined  star  of  the  sixth  magnitude.  The 
remarkable  fact  that  the  comet  had  attained  naked-eye 
visibility  when  discovered,  coupled  with  the  further  fact 
that  this  region  must  have  been  repeatedly  swept  over  by 
comet-seekers  to  within  a  few  days  of  its  discovery,  shows 
that  the  comet  must  have  rather  suddenly  attained  its 
conspicuous  visibility."  The  orbit  of  Holmes'  Comet  is 
almost  circular. 

138 


THE  SUN'S  FAMILY  OF  COMETS 

Another  well-known  comet  is  that  known  as  Brooks* 
Second  Periodic  Comet.  It  was  detected  in  1889,  and 
returned  again  to  perihelion  in  1896.  In  1903  it  was 
again  observed  much  fainter  than  before.  Mr.  Chambers 
remarks  in  connection  with  this  comet :  "  The  steady 
diminution  in  the  brightness  is  so  marked  that  it  is 
hazardous  to  predict  its  future.  At  its  last  return  it 
was  only  visible  in  some  of  our  largest  telescopes.  It  is 
due  to  return  in  1910,  and  again  in  1917.  Shall  we  see 
it  ?  Perhaps  we  shall ;  perhaps  we  shall  not.  But  if  we 
do  see  it  on  either  of  these  two  occasions,  it  will  still 
be  leading  a  threatened  life,  for  in  1921  it  will  again 
approach  very  close  to  Jupiter,  and  very  likely  that  may 
end  its  career ;  or  if  not,  it  will  certainly  lead  to  a  serious 
transformation  of  its  orbit." 

Besides  these  comets  of  short  period,  there  are  six 
comets  of  long  period :  WestphaPs,  revolving  round  the 
Sun  in  sixty-seven  years,  and  which  is  again  due  in  1913  ; 
Pens'  Comet,  revolving  in  seventy  years,  which  returned 
in  1883,  and  is  again  due  in  1955 ;  Di  Vico's,  revolving 
in  seventy-three  years,  which  is  due  in  1919  ;  Gibers1, 
revolving  in  seventy-four  years,  which,  first  seen  in  1815, 
returned  in  1887,  and  is  again  due  in  1960 ;  Brorsen's, 
with  a  period  of  almost  seventy-five  years,  which  is  due 
in  1922  ;.  and  finally,  Halley's,  already  referred  to. 

Thus  it  is  known  that  the  solar  system  contains 
certainly  thirteen  comets  of  short  period,  and  six  of 
long  period.  Besides,  it  is  believed  that  fourteen  other 
comets  are  also  periodic.  Their  periods  range  from  five 
to  nine  years,  but  they  have  not  been  proved  beyond 
a  doubt  to  belong  to  the  solar  system.  Besides  these 
periodic  comets  there  are  three,  LexelPs  Comet,  Di  Vico^s 
Comet,  and  Biela's  Comet,  which  were  once  periodic,  and 

139 


THE   SUN'S   FAMILY  OF  COMETS 

have  now  either  ceased  to  exist  or  have  been  deflected 
into  new  paths. 

The  first  named  was  discovered  by  Messier,  a  famous 
discoverer  of  comets,  on  June  14,  1770.  An  orbit  was 
calculated  for  it  by  a  Russian  mathematician  named 
Lexell,  who  assigned  to  it  a  period  of  five  and  a  half 
years.  It  was,  however,  never  seen  again.  Lexell  found 
that  in  1707  the  comet  had  passed  very  close  to  Jupiter, 
which  had  completely  altered  its  path ;  and  accordingly 
he  made  another  calculation,  to  the  effect  that  the 
comet  should  be  seen  in  1781,  but  again  he  was  doomed 
to  disappointment.  He  finally  concluded  that,  in  1779, 
Jupiter  had  again  altered  the  comet's  path  by  its  enormous 
attraction  when  the  flimsy  cometary  body  again  passed 
near  to  the  giant  planet.  LexelPs  Comet  has  never  since 
been  seen. 

In  1844  a  comet  was  detected  at  Rome  by  Di  Vico, 
and  an  orbit  was  assigned  of  1993  days.  The  comet, 
however,  was  never  seen  again.  The  most  remarkable 
case  of  all  was  that  of  Biela's  Comet,  which,  after  being 
known  for  years  as  a  member  of  the  Sun's  comet  family, 
disappeared  in  1852,  and  was  not  again  seen.  In  a 
future  chapter  this  comet,  which  is  the  key  to  our 
knowledge  of  the  nature  of  these  bodies,  will  be  fully 
discussed. 

The  comets  above  mentioned  are  those  which  belong 
to  the  Sun's  system.  The  great  majority  of  comets 
with  which  the  next  chapter  deals  have  not  been  proved 
to  belong  to  our  system,  and  many  of  them  seem  to 
be  only  visitors  from  the  depths  of  space. 


140 


CHAPTER   XIV 

THE   MESSENGERS   OF   SPACE 

THE  previous  chapter  dealt  with  those  comets  which 
are  known  to  belong  to  the  solar  system,  and  which 
are  thus  always  subject  to  the  influence  of  the  Sun. 
In  the  present  chapter  attention  is  directed  to  the  large 
comets,  which  are  either  visitors  to  the  solar  system 
from  the  depths  of  space  or  which,  if  they  do  revolve 
round  the  Sun,  move  out  to  distances  so  enormous  that 
we  cannot  with  certainty  pronounce  them  to  be  members 
of  the  Sun's  family.  Many  of  the  most  famous  comets 
which  have  ever  appeared  belong  to  these  two  classes. 

Some  of  the  comets  contained  in  the  second  class 
probably  belong  to  the  solar  system,  but  their  periods 
are  so  long  that  astronomers  do  not  know  whether  or 
not  they  will  ever  return.  For  instance,  the  second 
comet  of  1824  has  been  calculated  to  have  a  period 
of  millions  of  years,  the  first  comet  of  1863  has 
been  said  to  revolve  in  nearly  two  million  years,  the 
comet  of  1680  in  over  fifteen  thousand  years,  and  so  on  ; 
but  no  one  can  implicitly  trust  these  estimates,  as  much 
uncertainty  surrounds  them.  Such  comets  might,  in 
their  long  journey  in  space,  be  attracted  from  their  paths 
by  dark  stars  or  meteor  streams,  and  would  thus  be  lost 
for  ever  to  the  solar  system.  They  cannot  be  regarded  as 
permanent  members  of  the  solar  system. 

Most  of  the  really  grand  comets  which  have  been 
seen — with  the  exception  of  Halley's  Comet  at  its  appear- 

141 


THE   MESSENGERS   OF   SPACE 

ances — have  belonged  to  either  of  these  two  classes. 
The  comet  of  1264,  a  magnificent  object  which  was 
supposed  to  have  been  identical  with  the  comet  of  1556, 
was  expected  on  this  supposition  to  return  about  1858. 
But  it  was  not  seen  again,  and  consequently  it  is  doubtful 
if  the  two  comets  were  really  identical.  In  1264  popular 
superstition  fixed  on  the  comet  as  a  presage  of  the  death 
of  Pope  Urban  IV. 

A  remarkable  comet,  known  as  De  Cheseaux's  Comet, 
appeared  in  1744.  It  had  no  fewer  than  six  tails.  De 
Cheseaux,  the  discoverer,  has  left  a  very  detailed  descrip- 
tion of  the  object.  He  wrote  as  follows  : — "  The  sky 
was  quite  overcast  from  the  first  to  the  seventh  of  March, 
but  on  the  last-named  day  the  clouds  became  broken  and 
gave  us  some  hope  of  seeing  the  comet's  tail.  I  prepared 
myself  for  seeing  over  again  just  about  what  I  had  seen 
during  the  closing  days  of  February.  At  four  o'clock  on 
the  morning  of  March  8th,  I  went  downstairs  with  a 
friend  into  the  garden,  with  the  east  facing  us.  This 
friend,  walking  in  front  of  me,  startled  me  by  saying  that 
instead  of  two  tails  there  were  five.  I  hardly  believed 
him,  but  after  having  passed  from  behind  several  build- 
ings which  had  partly  concealed  the  eastern  horizon  from 
me,  I  did  indeed  see  five  tails.  .  .  .  Besides  these  five 
tails,  there  was  a  sixth."  This  was  probably  one  of  the 
most  remarkable  comets  ever  witnessed. 

The  great  comet  of  1811  was  in  many  ways  unique. 
Discovered  on  26th  March  1811,  it  was  last  seen  on 
August  17,  1812,  nearly  seventeen  months  later.  The 
tail,  when  seen  at  its  best  in  the  middle  of  October, 
stretched  into  space  for  the  distance  of  a  hundred  million 
miles,  while  its  breadth  was  fifteen  millions.  Measure- 
ments made  by  Herschel  indicated  that  the  diameter  of 

142 


THE   MESSENGERS   OF  SPACE 

the  nucleus  of  the  comet  was  428  miles.  A  famous 
German  astronomer  calculated  its  orbit,  and  estimated 
that  its  greatest  distance  is  fourteen  times  that  of  Nep- 
tune, and  its  period  over  three  thousand  years. 

Another  magnificent  comet  appeared  in  1843.  This 
was  described  as  "  a  grand  and  wonderful  sight  for  the 
extraordinary  distance  of  one-third  of  the  heavens,  the 
nucleus  being  perhaps  about  the  size  of  the  planet  Venus." 
This  remarkable  comet,  one  of  the  brightest  which  has 
ever  been  seen,  was  detected  in  the  end  of  February  1843, 
in  the  southern  hemisphere.  After  the  middle  of  March 
the  comet  became  visible  in  the  northern  hemisphere. 
The  remarkable  feature  about  the  comet  of  1843  was  its 
near  approach  to  the  Sun.  Its  central  portion  was 
within  78,000  miles  of  the  orb  of  day,  so  that  only  a 
little  over  thirty  thousand  miles  separated  the  surface  of 
the  Sun  and  the  comet.  The  result  of  this  near  approach 
was  that  the  comet  whirled  past  its  perihelion  point  at 
the  amazing  rate  of  366  miles  per  second.  In  two  hours 
and  eleven  minutes  it  described  half  of  the  curvature  of  its 
oval-shaped  orbit,  while,  as  one  astronomical  writer  has 
pointed  out,  "  in  travelling  over  the  remaining  half,  many 
hundreds  of  sluggish  years  will  doubtless  be  consumed." 
In  many  ways  the  comet  of  1843  was  a  remarkable  object. 
Its  tail  streamed  into  space  for  two  hundred  millions  of  miles. 

The  next  brilliant  comet  was  detected  by  Donati  at 
Florence  on  June  2,  1858,  as  a  little  round  nebulous 
mass,  very  faint,  in  the  constellation  Leo,  and  is  con- 
sidered by  most  astronomers  to  have  been  the  grandest 
comet  of  the  nineteenth  century.  At  first  no  one 
suspected  that  the  faint  little  telescopic  object  would 
develop  into  so  magnificent  a  stellar  spectacle  as  the 
comet  of  Donati.  In  the  middle  of  July  a  nucleus  de- 

143 


THE   MESSENGERS   OF   SPACE 

veloped.  In  the  middle  of  August  a  tail  began  to  make 
its  appearance,  and  by  the  beginning  of  September  it 
was  visible  to  the  unaided  eye.  By  the  twelfth  of  that 
month,  the  nucleus  of  the  comet  shone  with  a  brilliance 
equal  to  that  of  the  Pole  Star.  From  this  date  a 
magnificent  celestial  spectacle  was  assured.  Occupying  a 
favourable  position  in  the  northern  heavens,  it  was  in  a 
most  famous  position  for  observation.  "This  comet," 
as  Mr.  G.  F.  Chambers  has  pointed  out,  "  has  not  often 
been  equalled  in  the  intense  brilliance  of  its  nucleus,  and 
the  unusual  and,  so  to  speak,  artistic  configuration  of  its 
tail,  which  features  the  absence  of  the  Moon  in  the  early 
part  of  October,  enabled  spectators  to  view  to  the  very 
best  advantage.  The  passage  of  the  comet  in  front  of 
Arcturus  on  October  5th  will  ever  remain  treasured  in 
the  memory  of  those  who  saw  it."  The  late  Miss  Clerke 
confirms  this  estimate ;  she  says :  "  The  most  striking 
view  was  presented  on  October  5th,  when  the  brilliant 
star  Arcturus  became  involved  in  the  brightest  part  of 
the  tail,  and  during  many  hours  contributed,  its  lustre  un- 
diminished  by  the  interposed  nebulous  screen,  to  heighten 
the  grandeur  of  the  most  majestic  celestial  spectacle  of 
which  living  memories  retain  the  impress." 

The  comet  was  followed  by  astronomers  until  March  4, 
1859,  when  it  disappeared  from  the  view  of  the  largest 
telescopes  then  in  existence.  Various  estimates  have  been 
made  of  the  period,  such  as  1879  years  and  2040  years 
and  2138  years.  One  calculation  suggested  that  Donati's 
Comet  was  identical  with  a  famous  comet  which  appeared  in 
146  B.C.  and  is  mentioned  in  the  Chinese  annals.  But  the 
periods  calculated  are  very  uncertain.  Estimates,  probably 
correct,  have  been  made  of  the  dimensions  of  the  nucleus 
and  tail  of  the  comet.  The  tail  was  14,000,000  miles 

144 


THE   MESSENGERS   OF  SPACE 

long  on  30th  August,  and  seems  to  have  reached  its 
maximum  length  on  10th  October,  when  it  streamed  out- 
wards into  space  for  51,000,000  miles.  On  the  same 
day  the  nucleus  was  estimated  as  630  miles  in  diameter. 
The  comet  was  carefully  studied  by  astronomers  on  both 
sides  of  the  Atlantic.  Good  weather  prevailed  during 
its  nearest  approach  to  the  earth,  and  consequently  it 
was  thoroughly  and  exhaustively  studied. 

Three  years  later  another  brilliant  object,  perhaps  even 
more  remarkable  than  Donati's  Comet,  became  visible  to 
the  Earth's  inhabitants.  It  was  discovered  on  May  13, 
1861,  in  New  South  Wales,  and  on  llth  June  passed  its 
perihelion  point.  On  29th  June  it  became  visible  in  the 
northern  hemisphere.  The  following  description  was 
given  by  Sir  John  Herschel,  who  observed  it  from 
Hawkhurst,  in  Kent :  "  The  comet,  which  was  first  ob- 
served here  on  Saturday  night,  June  29th,  by  a  resident 
in  the  village  of  Hawkhurst,  became  conspicuously  visible 
on  the  30th,  when  I  first  observed  it.  It  then  far 
exceeded  in  brightness  any  comet  I  have  before  observed, 
those  of  1811  and  the  recent  splendid  one  not  except ed. 
Its  total  light  certainly  far  surpassed  that  of  any  fixed 
star  or  planet,  except  perhaps  Venus  at  its  maximum.11 

The  remarkable  fact  about  the  great  comet  was  that 
on  the  night  of  30th  June,  the  Earth  and  Moon  passed 
through  its  tail.  The  comet  was  at  the  time  between 
the  Earth  and  the  Sun,  fourteen  millions  of  miles  from  our 
planet,  while  its  tail  stretched  outwards  for  fifteen  millions 
of  miles.  The  passage  of  the  Earth  through  this  tail 
was  almost  imperceptible.  The  vast  majority  of  persons 
never  knew  that  such  an  event  had  taken  place,  and  even 
the  astronomers  noted  only  a  singular  phosphorescence 
in  the  sky.  Lowe,  a  meteorologist  of  the  day,  remarked 

145  K 


THE  MESSENGERS  OF  SPACE 

that  the  sky  had  a  yellow  auroral  aspect,  and  that  the 
Sun  gave  but  feeble  light  although  the  sky  was  cloudless, 
and  at  seven  o'clock  in  the  evening,  although  it  was  the 
midsummer  season,  artificial  lights  had  to  be  used.  The 
fact  that  our  world  passed  through  its  tail  and  that  the 
inhabitants  were  unaware  of  the  fact,  is  the  strongest  proof 
of  the  harmlessness  of  this  large  comet. 

The  comet  of  1874  discovered  by  a  French  astronomer 
named  Coggia,  at  Marseilles,  on  17th  April  1874,  and 
since  known  by  his  name,  was  much  less  brilliant  than  its 
predecessor  in  1861,  but  nevertheless  was  a  fine  celestial 
spectacle.  In  July  it  became  visible  to  the  unaided  eye. 
On  the  21st  of  that  month  it  was  at  its  nearest  point  to 
the  Earth,  a  distance  of  nine  millions  of  miles.  Various 
estimates  have  been  made  of  the  period  in  which  the 
comet  revolves.  One  calculation  assigned  a  period  of 
5711  years,  and  another  a  period  of  10,455  years. 

The  comet  of  1880,  seen  in  the  southern  hemisphere 
only,  was  one  of  the  most  remarkable  cometary  bodies. 
In  appearance  it  was  very  similar  to  the  great  comet  of 
184B,  and  when  its  orbit  was  calculated  it  was  found  to 
revolve  in  a  path  almost  identical  with  that  famous  body. 
Three  of  the  most  distinguished  calculators  investigated 
the  comet's  motions  independently,  and  each  found  the 
path  of  the  two  bodies  almost  identical.  Two  years 
later  another  great  comet  was  discovered  by  the  director 
of  the  Observatory  at  Rio  de  Janeiro.  It  soon  became 
a  magnificent  object  in  the  southern  hemisphere.  Sir 
David  Gill,  who  observed  it  from  the  Cape  Observatory, 
remarked  that  the  comet  "showed  an  astonishing  brilliancy 
as  it  rose  behind  the  mountains  to  the  east  of  Table  Bay. 
and  seemed  in  no  way  diminished  in  brightness  when  the 
Sun  rose  a  few  minutes  afterwards.  It  was  only  necessary 

146 


THE   MESSENGERS   OF   SPACE 

to  shade  the  eye  from  direct  sunlight  with  the  hand  at 
arm's  length  to  see  the  comet  with  its  brilliant  white 
nucleus  and  dense  white  sharply  bordered  tail  of  quite 
half  a  degree  in  length."  The  comet  passed  between  the 
Earth  and  the  Sun  on  the  17th  September,  and  on  the 
following  day  was  visible  in  full  sunlight  close  to  the  orb 
of  day.  In  Spain  it  was  seen  through  a  passing  cloud 
when  very  close  to  the  Sun. 

The  most  remarkable  feature  of  this  great  comet  was 
the  fact  that  its  orbit  showed  a  remarkable  resemblance 
to  the  great  comets  of  1843  and  1880.  Astronomers 
were  amazed  at  this  discovery.  It  was  at  least  possible 
that  the  comet  of  1880  was  a  return  of  that  of  1843  ; 
but  for  an  enormous  comet  to  return  in  only  two  years 
was  unthinkable.  As  the  late  Miss  Clerke  remarked, 
"  A  comet  which  at  a  single  passage  through  the  Sun's 
atmosphere  encountered  sufficient  resistance  to  shorten 
its  period  from  thirty-seven  to  two  years  and  eight 
months  must  in  the  immediate  future  be  brought  to  rest 
on  his  surface."  The  great  comet  was  kept  under  obser- 
vation for  about  six  months,  but  before  it  disappeared 
the  opinion  was  widespread  that  it  was  not  a  return  of 
the  comets  of  1843  and  1880.  In  1887  another  comet 
was  discovered  with  an  orbit  also  similar.  Now  the  only 
explanation  of  the  identity  of  these  orbits  is  that  each  of 
these  comets  were  fragments  of  a  larger  cometary  body 
which,  revolving  in  the  same  orbit,  had  been  gradually 
disrupted  into  a  number  of  different  comets — the  comets 
of  1668,  1843,  1880,  1882,  1887,  and  probably  also 
another  comet,  seen  in  1882.  This  is  proof  that  comets, 
unlike  the  planets,  are  not  lasting — that  they  are  liable  to 
be  dissipated  into  space.  This  much  may  be  gathered 
from  a  study  of  the  movements  and  orbits  of  comets. 

147 


THE   MESSENGERS   OF   SPACE 

Much  more  remarkable,  however,  is  the  information 
gained  by  a  study  of  their  physical  conditions. 

After  1882  no  very  brilliant  comet  was  visible  in 
the  northern  hemisphere,  although  in  1901  another 
bright  southern  comet  was  observed.  In  1902,  Perrine's 
Comet  was  faintly  visible  to  the  unaided  eye,  but 
too  faintly  to  attract  popular  attention.  The  appear- 
ance of  the  great  daylight  comet  of  1910  came  there- 
fore as  a  pleasant  surprise  not  only  to  astronomers, 
but  also  to  the  general  public.  On  January  15,  1910, 
the  Johannesburg  newspaper,  The  Leader,  informed  Mr. 
Innes,  director  of  the  Transvaal  Observatory,  that  they 
had  received  the  following  telegram  from  the  station- 
master  at  the  railway  station  at  Kopjes,  in  the  Orange 
Colony :  "  Halley's  Comet  was  seen  by  Fireman  Bourke, 
Driver  Tucker,  and  Guard  Marais  at  4.45  rising  in  front 
of  the  sun.  It  was  visible  for  about  twenty  minutes."" 

"The  railway  employees  had  seen  the  brilliant  object 
in  the  sunrise  before  the  astronomers  saw  it,  and  they 
thought  it  was  Halley's  Comet,  which  was  due  to  return  at 
that  time._  As  soon  as  the  comet  was  observed,  however, 
it  was  seen  that  it  could  not  be  Halley's.  Warned  by  this 
message  from  the  station-master,  we  kept  watch  on  the  next 
morning,  but  it  was  cloudy.  This  morning  (January  17) 
was  also  cloudy,  but  there  was  a  break  just  above  the  place 
of  sunrise.  At  5.29  standard  time  the  comet  was  seen." 

In  a  later  statement  Mr.  Innes  said  :  "  The  earliest  date 
on  which  this  comet  was  seen  in  South  Africa  appears 
to  be  on  Thursday,  January  12,  at  14  hours  25  minutes 
Greenwich  meantime,  by  some  workmen  at  the  Transvaal 
Premier  Diamond  Mine.  A  letter  from  Cullinan,  dated 
January  16,  informed  me  that  on  that  date  and  also  on 
Friday  morning  several  workmen  observed  the  comet." 

The  comet  soon  passed  the  Sun,  and  became  visible 
148 


THE   MESSENGERS   OF   SPACE 

in  the  evening  skies — a  magnificent  object,  which 
attracted  much  attention ;  and  had  it  not  been  for  the 
unfavourable  weather  in  Great  Britain  at  the  time,  a 
good  deal  more  would  have  been  seen  of  it.  On  the 
clear  evenings  the  comet  was  observed  and  admired  by 
the  average  man  and  closely  studied  by  the  astronomer. 
The  comet  was  observed  by  the  present  writer  at  Balerno, 
Mid-Lothian,  on  January  22  and  29,  observations  on  other 
dates  being  impossible  owing  to  the  unfavourable  weather. 
Seen  in  a  two-inch  refractor  on  January  29,  the  nucleus  was 
very  bright  and  well  defined,  while  the  head  presented  a 
resemblance  to  drawings  of  Coggia's  Comet  of  1874. 

Even  at  the  large  Observatories  it  was  difficult  to  get 
good  photographs,  owing  to  its  position  in  the  western 
sky  so  close  to  the  sunset  twilight.  The  spectrum  of 
the  comet  was  observed  by  Professor  Frost,  director  of 
the  Yerkes  Observatory,  on  January  24,  when  the  bright 
lines  of  sodium  characteristic  of  many  comets  were  noted. 
The  element  cyanogen  was  also  detected.  The  spectro- 
scopic  observations  indicated  that  on  January  27  the 
comet  was  receding  from  the  Earth  with  a  considerable 
velocity.  This  agrees  with  its  very  rapid  diminution  in 
brightness.  On  January  29  it  was  well  seen  ;  a  few  days 
later  it  was  practically  invisible. 

The  lines  addressed  to  the  "Stranger  of  Heaven," 
the  great  comet  of  1811,  by  the  "Ettrick  Shepherd,11 
seemed  specially  appropriate  to  the  comet  of  1910  : — 

' '  Stranger  of  heaven,  I  bid  thee  hail ! 
Shred  from  the  pall  of  glory  riven, 
That  flashest  in  celestial  gale 

Broad  pennon  of  the  King  of  Heaven. 

Whate'er  portends  thy  front  of  fire 
And  streaming  locks,  so  lovely  pale, 

Or  peace  to  man  or  judgment  dire, 
Stranger  of  Heaven,    Ibid  thee  hail  ! " 
149 


CHAPTER   XV 
THE  NATURE   OF   COMETS 

IN  the  two  previous  chapters  mention  was  made  of  the 
two  principal  classes  of  comets — comets  which  have 
been  proved  to  belong  to  the  solar  system,  and  those 
comets  which  either  belong  to  our  system,  revolving 
in  uncertain  periods,  or  only  pay  a  fleeting  visit  to 
the  planetary  regions,  dashing  away  again  into  space. 
Although  these  two  classes  differ  in  many  respects,  they 
only  differ  in  regard  to  their  orbits.  That  is  to  say,  all 
comets,  whether  they  belong  to  the  solar  system  or  not, 
are  alike  in  their  constitution  and  nature ;  and  in  this 
chapter  an  attempt  will  be  made  to  explain  the  compli- 
cated phenomena  connected  with  them. 

The  most  striking  feature  about  a  bright  comet  is  its 
tail.  As  remarked  in  a  previous  chapter,  telescopic 
comets  are  often  devoid  of  tails,  but  all  bright  comets 
are  distinguished  by  these  appendages,  and  consequently, 
to  the  average  man  and  the  casual  star-gazer,  a  comet  is 
only  of  interest  if  it  possesses  a  tail.  One  of  the  most 
notable  things  about  the  tails  of  comets  is  that  they  are 
always  pointed  away  from  the  Sun.  If  the  comet  is 
approaching  the  Sun,  the  tail  follows  the  head.  If  it  is 
receding  from  the  Sun,  the  head  follows  the  tail.  This 
is  a  remarkable  fact,  which  shows  that  comets  lack  the 
stability  which  characterises  the  planets.  For  many  years 
this  fact  puzzled  astronomers,  and  it  was  not  until  the 
beginning  of  last  century  that  any  progress  was  made 

150 


'.photograph  by  D, 


MOREHOUSE'S  COMET,  1908 


This  comet  attracted  a  great  deal  of  attention,  although  only  a  telescopic 
object.  The  agitation  in  the  matter  forming  the  tail  will  be  noticed  in  the 
photograph. 


THE  NATURE  OF  COMETS 

towards  an  explanation.  The  astronomer  Olbers,  of 
Bremen,  well  known  for  his  discovery  of  the  asteroids, 
explained  the  tails  of  comets  very  simply.  The  Sun  not 
only  attracts  comets  and  planets  to  itself,  but  its  light 
exercises  a  repulsive  power  on  minute  particles,  which  are 
thus  driven  off*  in  a  direction  opposite  to  the  Sun.  This 
theory  was  very  fully  elaborated  by  a  famous  Russian 
astronomer,  the  late  Professor  Bredikhine.  Bredikhine's 
researches  led  him  to  divide  the  tails  of  comets  into  three 
types.  The  first  of  these  consists  of  long  straight  tails, 
pointed  directly  away  from  the  Sun,  represented  by  the 
tails  of  the  comets  of  1811, 1843,  and  1861.  In  the  second 
of  these  types,  represented  by  those  comets  bearing  the 
names  of  Donati  and  Coggia,  the  tails,  although  on  the 
whole  pointed  away  from  the  Sun,  are  considerably 
curved.  The  tails  of  the  third  type  have  been  described 
as  "short,  strongly  bent,  brush-like  emanations,"  which 
in  bright  comets  "  seem  to  be  only  found  in  combination 
with  tails  of  the  higher  classes."  He  showed  that, 
probably,  tails  of  the  first  types  are  formed  of  hydrogen, 
those  of  the  second  of  hydrocarbon,  and  those  of  the  third 
of  iron,  with  a  mixture  of  sodium  and  some  other  elements. 

On  the  whole,  this  theory  is  considered  satisfactory. 
The  question,  however,  presents  itself, — What  is  this 
remarkable  repulsive  force  ?  There  seems  to  be  a  general 
agreement  among  the  scientists  that  the  force  is  electrical. 
It  only  affects  the  very  smallest  and  most  insignificant 
particles  of  matter,  and  this  explains  why  the  planets  and 
solid  bodies  are  not  affected  by  the  force.  It  has  also  been 
suggested  that  the  repelling  force  may  be  due  to  what  is 
called  "  light  pressure,"  the  action  of  rays  of  light  on  very 
minute  particles  of  matter. 

So  much  has  been  learned  of  the  nature  of  comets  by 
151 


THE   NATURE   OF  COMETS 

theory.  Most  of  our  knowledge  of  these  objects,  how- 
ever, is  due  to  direct  observation.  The  invention  of  the 
spectroscope,  about  the  middle  of  the  nineteenth  century, 
referred  to  in  a  previous  chapter,  resulted  in  a  consider- 
able increase  of  our  knowledge  of  comets  and  cometary 
phenomena.  It  was  shown  early  in  the  history  of  this 
line  of  research,  by  Donati  and  others,  that  the  light  of 
comets  is  partly  inherent  and  partly  reflected.  The  late 
Sir  William  Huggins,  the  late  Dr.  Copeland,  and  others, 
ascertained  the  existence  in  the  heads  of  comets  of  hydro- 
carbon gas,  and  this  has  been  since  confirmed  by  other 
observers.  These  observations,  of  course,  give  support  to 
Bredikhine's  theory  of  comets1  tails.  In  1882  this  theory 
was  still  further  confirmed  by  observations  which  the 
late  Dr.  Copeland  and  others  made  of  Wells'  Comet  of 
that  year.  On  May  27th,  Copeland  ascertained  the 
existence  of  sodium  in  the  comet.  This  was  the  first 
occasion  on  which  that  element  was  recognised  in  one 
of  these  bodies.  The  same  astronomer  also  recognised 
sodium  in  the  great  comet  of  1882. 

A  comet  which  contributed  materially  to  our  knowledge 
of  cometary  phenomena  was  that  discovered  on  September 
1, 1908,  by  Morehouse,  an  American  astronomer.  Observa- 
tions on  this  object^  reve#Jed  the  presence  of  the  poisonous  fl 
gas,  cyanogen,  which 'war  indeed  the  most  prominent  element 
in  the  comet,  and  which  dominated  its  spectrum.  Other 
remarkable  disclosures  were  made  by  this  comet.  A  large 
number  of  photographs  were  taken  at  the  Goodsell  Ob- 
servatory, Minnesota.  Professor  H.  C.  Wilson,  of  that  in- 
stitution, remarks  as  follows  on  this  comet :  "  While  the 
observer  was  guiding  the  telescope  for  these  photographs, 
the  portion  of  the  comet's  tail  which  was  in  the  field  of 
the  guiding  telescope  grew  visibly  fainter,  and  appeared  to 

152 


THE  NATURE  OF  COMETS 

detach  itself  from  the  head.  The  two  photographs  taken 
with  the  six-inch  camera  show  that  this  appearance  was 
real,  and  that  the  bright  part  of  the  tail  was  actually 
detached  from  the  head  of  the  comet  and  was  moving 
outward."  On  October  15,  a  bend  became  apparent  in 
the  main  tail,  which  photographs  showed  to  be  travel- 
ling rapidly  from  the  head.  "This  outward  motion," 
says  one  observer,  "  was  also  traceable  in  the  case  of 
several  knots  of  brightness  in  the  tail." 

Morehouse's  was  not  the  only  comet  which  was  ob- 
served to  break  up.  The  great  comet  of  1882  was  also 
seen  to  throw  off  portions  of  its  mass.  A  German 
astronomer  noted  on  5th  and  7th  October  of  that  year 
two  centres  of  condensations  in  the  comet,  while  on  the 
9th  of  the  same  month  Schmidt  detected  a  little  nebulous 
object  close  to  the  comet,  which  had  been  apparently 
thrown  off.  Professor  Barnard,  some  days  later,  glimpsed 
six  or  eight  little  cometary  masses  separate  from  the 
comet.  Another  instance  of  cometary  disruption  was 
afforded  by  Brooks'  Second  Periodic  Comet,  discovered  in 
1889.  About  a  month  after  its  discovery,  it  was  seen  to 
have  thrown  off  four  fragments.  In  his  interesting  work 
on  comets,  Mr.  Chambers  writes  as  follows : — "  Two  of 
these  were  very  faint  and  soon  disappeared,  but  the  other 
two  brignter  ones  were  miniatures  of  the  main  body,  each 
having  a  nucleus  and  a  tail.  For  a  while  they  moved 
away  from  their  primary.  In  three  weeks  the  nearer 
companion  ceased  to  recede ;  it  then  expanded  and  finally 
disappeared.  The  fainter  companion  continued  to  recede 
until  it  had  become,  a  month  from  discovery,  brighter 
than  the  parent  comet.  In  another  month  it  began  to 
approach  its  parent,  its  head  swelling  and  becoming  faint, 
the  tail  disappearing." 

153 


THE  NATURE  OF  COMETS 

It  is  probable  that  astronomers  have  learned  more  of 
the  constitution  and  nature  of  comets  from  one  small 
member  of  the  Sun's  family,  than  from  all  the  other 
comets — periodic  and  non-periodic — put  together.  On 
February  27,  1826,  Wilhelm  von  Biela,  an  amateur 
astronomer  at  Josephstadt,  in  Bohemia,  detected  a  faint 
comet  which  was  independently  noticed  ten  days  later  by 
a  French  observer,  Gambart,  at  Marseilles.  When  its 
orbit  was  calculated,  it  was  found  to  be  identical  with 
those  of  comets  which  appeared  in  1 772  and  1 805.  The 
comet  turned  out  to  be  a  periodic  one,  revolving  round 
the  Sun  in  a  period  of  between  six  and  seven  years.  Its 
return  was  predicted  for  1832,  and,  true  to  calculation,  it 
reappeared  in  that  year.  Its  reappearance  was  made  the 
occasion  of  a  "comet  scare.""  Certain  calculations  were 
made  which  seemed  to  show  that  portions  of  the  comet 
would  sweep  over  part  of  the  Earth's  orbit.  This  state- 
ment gave  rise  to  a  dread  lest  the  comet  should  strike 
the  Earth  and  our  world  be  destroyed.  A  panic  ensued 
among  the  ignorant,  especially  in  Paris,  and  the  popular 
excitement  was  not  cooled  until  the  director  of  the  Paris 
Observatory  announced  that  the  Earth  and  the  comet 
would  at  no  time  approach  within  fifty  million  miles  of 
each  other.  The  comet  was  not  seen  in  1839,  owing 
to  its  unfavourable  position  in  the  heavens,  but  on 
November  28,  1846,  it  was  re-discovered.  In  less  than  a 
month  it  was  seen  to  be  pear-shaped,  and  on  December  29 
and  early  in  January,  it  was  found  that  the  comet  had 
actually  separated  into  two  distinct  portions.  All  over 
the  world  astronomers  observed  the  comet  with  amaze- 
ment, for  this  was  the  first  occasion  within  the  memory 
of  man  on  which  a  comet  was  seen  to  divide  into  two 
portions.  The  comet  again  returned  in  1852.  The 

154 


THE  NATURE  OF  COMETS 

companion  comet  was  again  seen,  but  at  a  much  greater 
distance.  It  was  now  a  million  and  a  quarter  miles  from 
its  primary,  eight  times  its  distance  in  1846.  In  1859 
the  comet  was  not  observed,  but  this  was  not  considered 
remarkable,  as  it  was  in  that  year  unfavourably  placed 
for  observation.  However,  much  interest  was  displayed 
at  its  return  in  1866,  at  which  date  it  was  expected  to  be 
very  favourably  placed.  An  active  search  was  instituted, 
but  neither  Biela's  Comet  nor  its  little  companion  was 
seen.  The  comet  was  obviously  lost,  and  astronomers 
gave  up  hope  of  ever  seeing  it  again. 

But  an  extraordinary  thing  happened.  The  comet 
was  again  due  to  appear  in  1872.  It  was  not  visible, 
but  when  the  Earth  crossed  its  path,  on  the  night  of 
November  27,  there  was  a  magnificent  shower  of  shooting 
stars.  Beginning  shortly  after  sunset,  the  "  rain  of  fire," 
as  one  observer  called  the  display,  lasted  until  eleven 
o^clock.  Four  hundred  meteors  were  counted  in  a  minute 
and  a  half;  and  some  magnificent  fireballs  equal  in  size 
to  the  apparent  diameter  of  the  Moon  were  observed. 
The  Earth  had  not  collided  with  Biela's  comet,  but  it 
was  ploughing  its  way  through  the  wreckage  and  debris 
into  which  the  comet  had  dissolved. 

A  German  astronomer,  Klinkerfues,  observing  at 
Gottingen,  was  impressed  with  the  idea  that  Biela's 
Comet,  or  at  least  a  portion  of  it,  might  still  be  visible, 
and  concluded  that  if  it  were  to  be  seen  at  all,  it  would 
be  in  the  southern  hemisphere,  in  the  opposite  region  of 
the  heavens  from  the  point  from  which  the  meteors  had 
radiated.  Accordingly,  convinced  that  the  meteors  re- 
presented the  shattered  debris  of  the  comet,  and  believ- 
ing that  other  portions  of  it  might  still  be  in  existence, 
he  telegraphed  to  Pogson,  the  astronomer  at  Madras,  the 

155 


THE  NATURE   OF  COMETS 

following  message  :  "  Biela  touched  Earth  November  27, 
search  near  Theta  Centauri."  Pogson  promptly  turned 
his  telescope  to  that  portion  of  the  sky,  and  glimpsed  on 
December  2,  and  again  on  the  following  evening,  a  very 
faint  object,  which  he  at  first  took  for  Biela's  Comet  or 
its  companion.  It  was  shown,  however,  that  it  could  not 
have  been  either,  but  was  probably  another  fragment 
which  was  detached  at  an  earlier  date.  The  orbit  of 


FIG.  5.— Showing  how  the  Tail  of  a  Comet  is  directed 
away  from  the  Sun. 

Biela's  Comet  was  thus  shown  to  be  identical  with  the 
meteoric  shower  known  as  the  Andromedids,  and  another 
fine  shower  was  observed  in  1885,  when  the  Earth  again 
crossed  the  path  of  the  lost  comet. 

Biela's  Comet  therefore  no  longer  exists ;  it  has  been 
dissolved  into  fragments ;  and  with  some  of  these  frag- 
ments our  planet  collided  on  November  27,  1872,  with 
the  result  that  a  display  of  celestial  fireworks  took  place 

156 


A  SHOWER  OF  METEORS 

A  meteoric  shower  is  one  of  the  grandest  of  astronomical  spectacles.  Beginning 
with  a  display  of  one  or  two,  then  tens,  then  hundreds,  it  culminates  in  a  "rain  of 
fire."  Such  spectacles  were  witnessed  in  1833,  i£66,  and  1872.  The  meteors  all 


THE  NATURE   OF  COMETS 

which  has  seldom  been  surpassed.  Thus  we  see  that 
comets  die,  as  Kepler  said  three  centuries  ago.  Unlike 
the  planets,  they  are  not  lasting,  but  break  up  into  small 
particles  of  matter,  which,  when  they  enter  our  Earth's 
atmosphere,  become  ignited  with  the  friction  of  the 
atmosphere  and  appear  in  the  form  of  shooting  stars. 

To  sum  up,  we  know  that  comets  are  bodies  of  extreme 
tenuity.  Stars  are  usually  to  be  seen  shining  through 
them  undimmed,  and  although  they  are  of  enormous  bulk 
they  have  practically  no  weight.  That  is  to  say,  they 
exercise  no  disturbing  influences  on  the  motions  of  the 
planets.  In  all  these  points  comets  differ  from  planets. 
And  as  already  mentioned,  there  is  another  important 
point  of  difference.  Although  nothing  in  the  changing 
Universe  can  be  called  eternal,  the  Sun  and  planets  are 
certainly  lasting  bodies,  but  comets  are  not  lasting. 
Even  in  the  short  period  of  man's  life,  comets  have  been 
seen  to  break  up  and  disappear. 

An  admirable  summary  of  our  knowledge  of  comets  is 
given  by  Mr.  E.  W.  Maunder  as  follows  : — "  Though  the 
bulk  of  comets  is  huge,  they  contain  extraordinarily  little 
substance.  Their  heads  must  contain  some  solid  matter, 
but  it  is  probably  in  the  form  of  a  loose  aggregation  of 
stones  enveloped  in  vaporous  material.  There  is  some 
reason  to  suppose  that  comets  are  apt  to  shed  some  of 
these  stones  as  they  travel  along  their  paths,  for  the 
orbits  of  the  meteors  that  cause  our  greatest  star  showers 
are  coincident  with  the  paths  of  comets  that  have  been 
observed.  But  it  is  not  only  by  shedding  its  loose  stones 
that  a  comet  diminishes  its  bulk  ;  it  also  loses  through 
its  tail.  As  the  comet  gets  close  to  the  Sun,  its  head 
becomes  heated  and  throws  off  concentric  envelopes,  much 
of  which  consists  of  matter  in  an  extremely  fine  state  of 

157 


THE  NATURE   OF  COMETS 

division.""  Mr.  Maunder  goes  on  to  show  that  for  a  par- 
ticle of  matter  less  than  the  one-twenty-five-thousandth 
part  of  an  inch  in  diameter,  the  repulsive  force  of  the 
Sun^s  light  is  greater  than  the  attractive  force  of  the 
central  orb  itself.  "  Particles  in  the  outer  envelope  of 
the  comet  below  this  size  will  be  driven  away  in  a  con- 
tinuous stream,  and  will  form  that  thin  luminous  fog 
which  we  see  as  the  comet's  tail." 

Thus  comets  lose  in  bulk  and  mass  through  their 
heads  and  their  tails.  Of  the  subsequent  history  of  the 
"  luminous  fog "  driven  off  by  the  repelling  power  we 
know  nothing,  but  of  the  loose  stones  shed  by  the  head 
we  know  a  great  deal.  To  a  consideration  of  these  loose 
stones  the  next  chapter  will  be  devoted. 


158 


CHAPTER   XVI 
THE  SHOOTING   STARS 


a  night  passes  without  the  recurrence 
of  a  celestial  phenomenon  familiar  to  the  most 
casual  star-gazer.  As  Flammarion  puts  it  in  his 
picturesque  language  :  "  Sometimes  when  night  has  silently 
spread  the  immensity  of  her  wings  above  the  weary 
earth,  a  shining  speck  is  seen  to  detach  itself  in  the 
shades  of  evening,  from  the  starry  vault,  shooting  brightly 
through  the  constellations  to  lose  itself  in  the  infinitude 
of  space."  These  "shining  specks"  are  known  variously 
as  shooting  stars,  falling  stars,  and  meteors.  The  latter 
term  is  the  most  scientifically  accurate,  because  the 
"shining  specks"  are  not  stars.  While  the  so-called 
"  fixed  stars  "  are  huge  globes,  some  exceeding  the  Sun 
in  size  at  enormous  distances  from  the  Earth,  the  shooting 
stars  are  merely  little  stones  and  particles  of  matter  a 
few  miles  above  the  surface  of  our  planet.  It  must 
always  be  borne  in  mind,  therefore,  that  the  titles  "  shoot- 
ing stars  "  and  "  falling  stars  "  are  incorrect,  and  that  it 
is  more  accurate  to  refer  to  these  objects  as  meteors. 
Scarcely  a  night  passes  without  one  or  more  of  these 
meteors  being  seen.  During  the  day,  too,  there  are 
probably  as  many  entering  our  atmosphere  and  flashing 
across  the  sky  as  at  night  ;  but  owing  to  the  sunlight 
they  are  unobserved.  It  has  been  calculated  that  every 
twenty-four  hours  the  dust  of  four  hundred  million 
meteors  falls  to  the  surface  of  the  Earth. 

159 


THE   SHOOTING   STARS 

On  most  evenings  meteors  are  observed  in  twos  or 
threes.  On  some  evenings  more  are  to  be  seen  than  on 
others.  On  some  occasions,  however,  these  meteors  are 
to  be  seen  not  in  twos  or  threes,  but  in  dense  showers. 
In  1799,  for  instance,  a  bright  shower  of  meteors  was 
observed  in  South  America  by  the  famous  Humboldt. 
On  the  night  of  November  12-13, 1833,  there  was  observed 
perhaps  the  finest  display  of  shooting  stars  ever  witnessed 
by  man.  It  was  best  seen  in  North  America,  and  during 
the  maximum  it  was  quite  impossible  to  count  the  number 
of  meteors  which  flashed  across  the  sky.  It  was  estimated 
that  their  frequency  was  about  half  that  of  snowflakes 
in  an  ordinary  snowstorm.  It  was  calculated  in  fact  that 
no  fewer  than  240,000  meteors  were  visible.  Observa- 
tions made  on  that  memorable  occasion  showed  that  the 
paths  of  all  the  meteors  traced  backwards  in  the  sky, 
intersected  at  a  point  in  the  constellation  Leo.  That 
is  to  say,  the  meteors  radiated  from  a  point  in  that  star 
group.  Hence  this  point  was  called  the  radiant  point, 
and  the  star  shower  was  called  the  Leonid  display.  On 
the  occasion  of  this  great  display,  the  meteors  struck 
terror  into  the  hearts  of  the  ignorant,  especially  the 
negroes  on  the  plantations  in  the  Southern  States,  who 
believed  the  end  of  the  world  to  be  at  hand. 

The  fact  that  thirty-four  years  had  elapsed  since  the 
magnificent  star  shower,  led  astronomers  to  expect  another 
display  about  1866  or  1867.  An  American  astronomer, 
the  late  Professor  H.  A.  Newton,  undertook  a  search 
through  the  ancient  records  to  see  if  he  could  find  traces 
of  star  showers  at  intervals  of  thirty-three  or  thirty-four 
years.  His  search  was  successful,  and  he  predicted  a 
star  shower  on  the  evening  of  November  13  and  morning 
of  November  14,  1866.  At  the  same  time  it  was  noted 

160 


A  FIREBALL  OR  BOLIDE 

These  objects,  known  as  bolides  or  fireballs,  and  the   larger  ones  as  aerolites, 
occasionally  visible,  and  form  superb  and  celestial  spectacles. 


THE   SHOOTING   STARS 

that  meteors  were  to  be  seen  yearly  in  varying  quantities 
radiating  from  the  same  point  in  Leo. 

Professor  Newton's  prediction  was  fulfilled.  On  the 
evening  of  November  13,  there  was  a  magnificent  display 
of  meteors — inferior,  it  is  true,  to  that  of  1833,  but  still 
magnificent.  In  his  book,  "  In  Starry  Realms,"  Sir  Robert 
Ball  has  given  an  excellent  account  of  this  fall  of  meteors, 
which  he  observed  from  Lord  Rosse's  Observatory,  Birr 
Castle,  Ireland,  where  he  was  at  the  time  employed  as 
astronomer  to  that  nobleman.  "  The  memorable  night," 
says  Sir  Robert  Ball,  "  was  a  very  fine  one  ;  the  Moon  was 
absent,  a  very  important  consideration  in  regard  to  the 
effectiveness  of  the  display.  The  stars  shone  out  clearly, 
and  I  was  diligently  examining  some  faint  nebulae  in 
the  eyepiece  of  the  great  telescope,  when  a  sudden  ex- 
clamation from  the  attendant  caused  me  to  look  up  from 
the  eyepiece,  just  in  time  to  catch  a  glimpse  of  a  fine 
shooting  star,  which,  like  a  great  sky-rocket,  but  without 
its  accompanying  noise,  shot  across  the  sky  over  our 
heads.  About  this  time  I  was  joined  at  the  telescope 
by  Lord  Oxmantown  (afterwards  Earl  of  Rosse),  and  we 
resumed  our  observations  of  the  nebulae,  but  a  grander 
spectacle  soon  diverted  our  attention  from  these  faint 
objects.  The  great  shooting  star  which  had  just  appeared 
was  merely  the  herald  announcing  the  advent  of  a  mighty 
host.  At  first  the  meteors  came  singly,  and  then,  as  the 
hours  wore  on,  they  arrrived  in  twos  and  in  threes,  in 
dozens,  in  scores  and  in  hundreds.  Our  work  at  the 
telescope  was  forsaken  ;  we  went  to  the  top  of  the  castel- 
lated walls  of  the  great  telescope,  and  abandoned  our- 
selves to  the  enjoyment  of  the  gorgeous  spectacle.  To 
'  number  the  meteors  baffled  all  our  arithmetic ;  while  we 
strove  to  count  on  the  one  side,  many  of  them  hurried 

161  L 


THE   SHOOTING   STARS 

by  on  the  other.  The  vivid  brilliance  of  the  meteors  was 
sharply  contrasted  with  the  silence  of  their  flight." 

In  1867,  another  shower,  much  feebler  than  that  of 
1866,  was  seen,  and  as  the  years  passed  on  the  display 
became  fainter,  until  the  number  of  meteors  seen  on  the 
particular  night  in  November  was  normal.  A  display  was 
predicted  for  1899,  in  accordance  with  the  thirty-three 
year  period,  but,  to  the  great  surprise  and  disappoint- 
ment of  astronomers,  nothing  was  seen.  In  1900  there 
was  no  better  success.  In  November  1901  there  was 
a  fairly  good  shower  observed  in  America,  but  vastly 
inferior  to  those  of  1833  and  1866.  Finally,  in  1904 
there  was  a  fairly  good  display  visible  in  Scotland.  The 
writer  observed  the  display  at  Balerno,  in  Mid-Lothian, 
and  noted  a  considerable  number  of  bright  meteors. 
The  shooting  stars  were  not  numerous,  but  they  were 
brilliant,  and,  in  short,  the  display  was  much  above  the 
normal.  Since  1904,  the  November  meteors  have  been 
few,  about  the  usual  number  being  observed. 

There  is  another  well-known  shower  of  meteors.  This 
is  the  Perseids,  so  called  from  the  fact  that  the  meteors 
appear  to  radiate  from  the  constellation  Perseus.  These 
are  to  be  seen  in  varying  numbers,  between  the  9th  and 
llth  of  August  every  year.  Unlike  the  Leonids,  they 
have  no  well-defined  period  of  greatest  number  and 
brilliance.  Other  two  important  showers  are  known,  the 
Lyrids,  seen  in  April,  which  appear  to  radiate  from  Lyra, 
and  the  Andromedids,  which  are  to  be  seen  towards  the  end 
of  November.  Many  minor  showers  are  known,  but  they 
are  too  faint  and  insignificant  to  attract  general  attention. 
When  it  was  found  that  the  Leonid  meteors  reached  a 
maximum  every  thirty-three  years,  astronomers  sought 
for  an  explanation  of  this  remarkable  fact.  Professor 

162 


THE   SHOOTING  STARS 

Adams,  one  of  the  discoverers  of  Neptune,  showed  that 
these  minute  Leonid  meteors  revolved  round  the  Sun  in  a 
well-defined  orbit  in  a  period  of  thirty-three  years,  and 
that  the  orbit  intersected  that  of  our  planet.  It  thus  be- 
came apparent  that  meteors  were  distributed  all  round  the 
orbit,  but  that  there  was  a  main  swarm  where  the  meteors 
were  closely  crowded  together,  and  which,  when  crossing 
the  Earth's  orbit,  was  ploughed  through  by  our  planet 


S-     •  •• 


FIG.  6. — Passage  of  the  Earth  through  the  thickest  portion  of  a 
Meteor  Swarm.  The  Earth  and  the  Meteors  are  here  represented 
as  approaching  each  other  from  opposite  directions. 

on  its  journey  round  the  Sun.  The  failure  of  the  main 
swarm  to  encounter  the  Earth  in  1899  was  a  source  of 
much  difficulty  to  astronomers.  However,  the  general 
opinion  seems  to  be  either  that  the  swarm  has  become 
greatly  worn  out  and  extended  along  its  orbit,  or  else 
that  it  was  slightly  deflected  from  its  path  by  the  action 
of  some  of  the  planets. 

The  most  remarkable  feature  of  the  November  meteors, 
however,  was  disclosed  in  1866  by  Professor  Schiaparelli. 

163 


THE   SHOOTING  STARS 

Having  calculated  the  orbit  of  the  meteors,  he  was  im- 
pressed by  its  identity  with  the  orbit  of  a  comet,  known  as 
Tempers  Comet,  which  revolves  round  the  Sun  in  thirty- 
three  years  and  which  was  seen  in  1866.  Then,  investi- 
gating the  orbit  of  the  August  meteors,  he  found  it  to 
coincide  with  that  of  a  bright  comet  which  appeared  in 
1862.  Finally,  there  came  the  discovery  that  the  lost 
comet  of  Biela  travelled  in  the  same  orbit  as  the  Andro- 
medids.  Thus  it  was  shown  that  the  shooting  stars  so 
familiar  to  the  Earth's  inhabitants,  and  so  long  a  mystery, 
were  nothing  less  than  the  appendages  of  comets.  Pro- 
fessor Schiaparelli  says :  "  The  meteoric  currents  are  the 
products  of  the  dissolution  of  comets,  and  consist  of 
minute  particles,  which  certain  comets  have  abandoned 
along  their  orbits  by  reason  of  the  disintegrating  force 
which  the  Sun  and  planets  exert  on  the  rare  materials  of 
which  they  are  composed." 

There  must  be  thousands  of  these  meteoric  currents 
in  the  solar  system,  and  large  numbers  must  cross 
the  orbits  of  the  other  planets  and  encounter  the 
various  orbs.  The  result  of  this  is  that  the  Earth  and 
the  other  planets  are  gradually  increasing  in  size  owing 
to  the  constant  fall  of  meteoric  matter.  None  of  the 
ordinary  shooting  stars,  of  course,  reach  the  ground  whole. 
They  are  reduced  to  dust,  which  falls  imperceptibly  to  the 
surface  of  the  Earth. 

There  is  another  class  of  much  larger  meteoric  bodies, 
and  numbers  of  them  fall  to  the  ground  without  being 
reduced  utterly  to  vapour.  These  are  known  variously 
as  uranoliths,  bolides,  and  aerolites.  From  ancient 
times  there  were  traditions  of  the  fall  of  stones  from 
the  sky,  but  it  was  not  until  1803  that  men  of  science 
came  to  believe  in  such  phenomena.  In  that  year  an 

164 


THE   SHOOTING   STARS 

aerolite  fell  at  Laigle,  in  the  department  of  the  Orne,  in 
France.  A  great  aerolite,  moving  from  south-west  to 
north-east,  perceived  at  Alencon,  Caen,  and  Falaise, 
suddenly  exploded  with  a  frightful  noise,  and  a  number  of 
meteoric  stones,  of  which  the  largest  weighed  20  Ibs.,  were 
thrown  to  the  ground,  and  were  picked  up  still  smoking. 
On  July  23,  1872,  on  a  beautiful  summer's  day,  an 
aerolite  fell  in  France,  after  a  tremendous  explosion  which 
was  heard  for  fifty  miles  round.  It  weighed  no  less  than 
126  Ibs.,  and,  by  the  force  of  its  fall,  dug  a  hole  over  five 
feet  in  depth.  In  April  1873,  another  great  bolide  fell 
near  Rome.  It  had  a  velocity  of  thirty-seven  miles  a 
second  on  arrival  in  the  Earth's  atmosphere,  and  it  was 
shattered  to  fragments.  At  Rowton,  in  Shropshire,  on 
April  20,  1876,  a  piece  of  iron  fell  and  buried  itself  in  a 
field.  When  dug  out,  it  was  still  hot.  This,  which  is 
known  as  "  the  Rowton  siderite,"  is  now  preserved  in  the 
British  Museum.  In  1881,  a  stone  weighing  three  pounds 
fell  in  Yorkshire  on  the  railway  line,  and  made  a  hole 
eleven  inches  deep.  On  November  23,  1877,  a  meteorite 
exploded  with  a  loud  report  over  the  town  of  Chester. 
A  famous  meteorite,  which  did  not  fall  to  the  ground  as  a 
solid  mass,  was  seen  in  December  21,  1876,  in  Kansas. 
It  is  thus  described  by  Professor  Howe,  an  American 
astronomer :  "  A  superb  fireball  appeared  over  the  State 
of  Kansas,  and  moved  thence  eastward  south  of  Chicago, 
across  Indiana  over  Lake  Erie,  to  Lake  Ontario,  where 
it  disappeared.  When  nearly  two  hundred  miles  from 
Bloomington,  Indiana,  the  meteor  burst,  and  the  inhabi- 
tants of  that  city  saw  a  magnificent  array  of  fireballs 
sweeping  through  the  evening  sky.  After  the  excitement 
aroused  by  the  marvellous  spectacle  was  over,  there  came 
a  tremendous  crack  like  the  reverberations  of  thunder. 

165 


THE   SHOOTING   STARS 

The  concussion  which  accompanied  it  led  some  to 
think  that  a  light  earthquake  had  shaken  the  town. 
How  terrific  must  a  detonation  have  been,  which 
was  so  startling  two  hundred  miles  away,  after  the 
sound  waves  had  been  on  their  journey  a  quarter  of 
an  hour.11 

There  has  been  much  controversy  among  the  astrono- 
mers as  to  the  exact  nature  of  these  aerolites  and  fireballs. 
Laplace  suggested  about  a  hundred  years  ago  that  they 
might  have  been  ejected  from  the  volcanoes  on  the  Moon  ; 
but  this  theory  was  soon  abandoned,  as  was  also  a  sug- 
gestion that  they  were  ejected  from  the  Sun.  Sir  Robert 
Ball  and  a  number  of  other  astronomers  believe  that 
these  aerolites  were  ejected  many  ages  ago  by  the  vol- 
canoes on  the  Earth's  surface,  then  much  more  powerful 
and  active  than  at  present,  and  that  they,  having  once 
been  thrown  out  from  our  planet,  would  intersect  the 
terrestrial  orbit  at  each  revolution.  The  alternative 
theory,  supported  by  Professor  Schiaparelli,  Sir  Norman 
Lockyer,  and  others,  regards  aerolites  as  simply  larger 
members  of  meteor  swarms,  fragments  of  comets.  This 
is  confirmed  by  the  fact  that  chemists  have  made  analyses 
of  the  elements  in  these  bodies  raised  to  incandescence, 
and  the  presence  has  been  detected  of  hydrocarbons, 
present  also  in  comets.  On  the  other  hand,  it  is  remark- 
able that,  with  one  exception,  an  aerolite  was  never 
seen  to  fall  to  the  ground  during  a  meteoric  shower. 
The  exception  took  place  on  November  27,  1885,  when 
during  a  shower  of  Andromedid  meteors,  a  large  bolide, 
weighing  more  than  8  Ibs.,  fell  at  Mazapil  in  Mexico. 
Whether  it  was  connected  with  the  showers  is  not 
known. 

The  study  of  meteors  has  made  great  progress  within 

166 


THE   SHOOTING   STARS 

the  last  thirty  years,  thanks  mainly  to  the  work  of  a 
single  observer,  Mr.  W.  F.  Denning  of  Bristol,  the  well- 
known  English  amateur  astronomer.  From  1872  to  1903, 
Mr.  Denning  determined  the  radiant  points  of  1172 
meteor  showers.  In  addition,  he  published  in  1899  a 
catalogue  of  the  radiant  points  of  meteors  numbering 
4367.  Thanks  to  Mr.  Denning's  work,  the  observation  of 
meteors  is  a  recognised  branch  of  astronomy,  and  may  be 
studied  by  any  one  who  is  interested  in  the  subject  and 
can  make  good  observations. 

A  word  may  be  said  here  of  a  phenomenon  closely  allied 
to  the  subject  of  meteors — the  Zodiacal  Light.  This  is  a 
phenomenon  which  is  much  better  seen  in  tropical  than 
in  temperate  regions,  but  it  is  occasionally  observed  in 
Europe.  A  pearly  glow  is  observed  in  the  spring  to 
spread  over  a  portion  of  the  sky  just  where  the  Sun  has 
disappeared.  In  autumn  the  same  thing  is  also  to  be 
seen  before  sunrise.  It  is  in  tropical  regions,  however, 
that  it  is  seen  in  its  full  glory.  Instead  of  being  seen 
like  a  cone,  as  in  temperate  regions,  it  appears  as  a  band 
of  light.  The  portions  nearest  to  the  Sun  are  equal  to 
the  Milky  Way  in  brilliance,  while  the  more  distant 
parts  are  much  fainter,  and  are  only  visible  owing  to 
the  clearness  and  purity  of  the  atmosphere  in  the 
tropics. 

The  exact  nature  of  the  Zodiacal  Light  has  long  been 
more  or  less  a  mystery,  but  it  seems  to  be  generally 
believed  among  astronomers  that  the  light  is  due  to 
diffused  dust,  probably  meteoric  matter  forming  an  outer 
appendage  to  the  Sun.  Opposite  in  the  heavens  is  a 
much  fainter  phenomenon,  generally  known  by  its  German 
name  of  the  "  Gegenschein "  or  counter-glow,  probably 
also  of  meteoric  composition. 

167 


THE   SHOOTING   STARS 

Our  survey  of  the  solar  system  commenced  with  the 
infinitely  great,  the  mighty  orb  of  the  Sun  itself,  and  it 
has  fittingly  closed  with  a  description  of  the  infinitely 
little,  the  minute  particles  of  cosmical  dust  which  move 
round  the  central  orb  in  obedience  to  the  law  of  gravita- 
tion. 


168 


THE  ZODIACAL  LIGHT 

A  pearly  radiance  which  is  observed  before  sunset  in  spring  and  before  sunrise 
in  autumn.  It  is  seen  in  all  its  glory  in  tropical  regions.  It  is  supposed  to  be 
due  to  meteoric  matter  beyond  the  Earth's  orbit. 


CHAPTER   XVII 
ECLIPSES   AND   TRANSITS 

IN  previous  chapters  a  brief  survey  has  been  made 
of  the  solar  system — the  Sun  and  its  family  of 
planets  and  the  comets  and  meteoric  swarms.  But 
before  passing  to  a  consideration  of  the  vast  universe 
outside  of  the  solar  system,  it  is  well  to  consider  the 
phenomena  which  arise  from  the  movements  of  the 
various  planets  and  the  inclination  of  their  orbits  round 
the  Sun.  These  facts  give  rise  to  the  two  classes  of 
kindred  phenomena  known  as  eclipses  and  transits.  We 
cannot  properly  understand  the  cause  of  the  periodic 
occurrences  known  as  eclipses  until  we  fully  realise  the  fact 
that  every  body  shining  by  reflected  light  casts  a  shadow 
into  space  in  a  direction  opposite  to  the  source  of  illu- 
mination. Thus  the  Earth  casts  a  shadow,  and  the 
Moon  casts  a  shadow.  Similarly  Mars,  Jupiter,  Saturn, 
Venus,  and  the  other  planets  cast  shadows.  But  it  is  the 
shadows  of  the  Earth  and  the  Moon  which  cause  the 
phenomena  known  to  the  Earth's  inhabitants  as  eclipses 
of  the  Moon  and  eclipses  of  the  Sun.  The  Earth  casts  a 
shadow  into  space ;  and  when  the  Moon,  the  Earth,  and  the 
Sun  are  in  a  line  with  the  Earth  in  the  centre,  the 
shadow  of  the  Earth,  which  extends  to  and  beyond  the 
orbit  of  the  Moon,  is  thrown  in  the  direction  of  our 
satellite.  If  the  Moon's  orbit  were  exactly  in  the  same 
plane  or  level  as  that  of  the  Earth,  our  satellite  would 
pass  at  every  revolution  through  the  shadow.  In  other 

169 


ECLIPSES  AND  TRANSITS 

words,  the  Moon  would  be  totally  eclipsed  and  would 
become  altogether  invisible  every  time  it  reached  the 
full  phase.  As  a  matter  of  fact,  however,  the  Moon's 
orbit  is  not  exactly  in  the  same  plane  as  that  of  the 
Earth,  and  it  is  only  occasionally  that  an  eclipse  does 
take  place.  Sometimes  an  eclipse  of  the  Moon  is  total — 
that  is  to  say,  the  Moon  is  completely  immersed  in  the 
Earth's  shadow — and  sometimes  only  partial,  a  portion  of 
the  Moon's  disc  remaining  outside  the  true  shadow.  A 
total  eclipse  of  the  Moon  is  a  very  striking  and  beautiful 
phenomenon.  As  the  Moon  becomes  more  and  more 
immersed  in  shadow,  the  illuminated  portion  becomes 
smaller  and  smaller  until  it  completely  disappears.  The 
Moon  is  not,  however,  usually  totally  invisible.  It  gene- 
rally assumes  a  dark  copper-coloured  hue,  caused  by  the 
refraction  of  sunlight  through  the  atmosphere  of  the 
Earth.  This  is  believed  to  be  due  to  the  fact  that  the 
blue  rays  of  the  Sun  are  absorbed  in  passing  through 
the  atmosphere  of  the  Earth,  just  as  the  sunset  and 
sunrise  skies  are  seen  to  assume  a  ruddy  colour. 

The  Moon,  however,  does  not  always  assume  this  tint 
during  eclipses  ;  sometimes  there  is  a  phenomenon  known  as 
the  "  black  eclipse,"  when  the  Moon's  surface  is  seen  with  a 
greyish-blue  tint.  Indeed,  sometimes  the  Moon  disappears 
altogether  during  eclipse.  These  variations  are  explained 
by  a  well-known  astronomer  in  the  following  remarks : 
"  It  has  been  suggested  that  if  the  portion  of  the  Earth's 
atmosphere  through  which  the  Sun's  rays  have  to  pass  is 
tolerably  free  from  aqueous  vapour,  the  red  rays  will  be 
absorbed,  but  not  the  blue  rays ;  and  the  resulting  illu- 
mination will  either  only  render  the  Moon's  surface  visible 
with  a  greyish-blue  tinge,  or  not  visible  at  all.  This  will 
yield  the  '  black  eclipse.' r 

170 


ECLIPSE  OF  THE  MOON 

Few  celestial  spectacles  visible  to  observers  in  Britain  are  more  striking  than 
eclipses  of  the  moon.  The  above  represents  the  shadow  creeping  gradually  over 
the  bright  disc  of  our  satellite. 


ECLIPSES   AND  TRANSITS 

Eclipses  of  the  Moon  have  long  been  a  source  of  terror 
to  the  unlearned,  and  especially  to  savage  tribes.  Many 
instances  might  be  given  of  the  fear  which  the  darkening 
of  the  Moon's  light  struck  into  the  hearts  of  the  ignorant. 
But  one  instance  will  suffice.  An  eclipse  of  the  Moon  took 
place  when  Columbus  was  in  the  island  of  Jamaica  in  1504. 
The  eclipse  was  total,  and  occurred  very  soon  after  sunset, 
and  the  event  occurred  at  a  most  convenient  time  so  far 
as  the  great  explorer  was  concerned.  In  the  "Life  of 
Columbus,1"  by  Sir  A.  Helps,  the  narrative  is  told  as 
follows : — 

"  The  Indians  refused  to  minister  to  their  wants  any  longer  ; 
and  famine  was  imminent.  But  just  at  this  last  extremity, 
the  admiral,  ever  fertile  in  devices,  bethought  him  of  an 
expedient  for  re-establishing  his  influence  over  the  Indians. 
His  astronomical  knowledge  told  him  that  on  a  certain  night 
an  eclipse  of  the  Moon  would  take  place.  One  would  think 
that  people  living  in  the  open  air  must  be  accustomed  to  see 
such  eclipses  sufficiently  often  not  to  be  particularly  astonished 
at  them.  But  Columbus  judged — and  as  the  event  proved, 
judged  rightly — that  by  predicting  the  eclipse  he  would  gain 
a  reputation  as  a  prophet,  and  command  the  respect  and  the 
obedience  due  to  a  person  invested  with  supernatural  powers. 
He  assembled  caciques  of  the  neighbouring  tribes.  Then  by 
means  of  an  interpreter,  he  reproached  them  with  refusing  to 
continue  to  supply  provisions  to  the  Spaniards.  'The  God 
who  protects  me/  he  said, '  will  punish  you.  You  know  what 
has  happened  to  those  of  my  followers  who  have  rebelled 
against  me,  and  the  dangers  which  they  encountered  in  their 
attempt  to  cross  Haiti,  while  those  who  went  at  my  command 
made  the  passage  without  difficulty.  Soon,  too,  shall  the 
divine  vengeance  fall  on  you  ;  this  very  night  shall  the  Moon 
change  her  colour  and  lose  her  light,  in  testimony  of  the  evils 
which  shall  be  sent  upon  you  from  the  skies/ 

' ( The  night  was  fine :  the  Moon  shone  down  in  full  bril- 
liancy. But  at  the  appointed  time  the  predicted  phenomenon 
took  place,  and  the  wild  howls  of  the  savages  proclaimed 
their  abject  terror.  They  came  in  a  body  to  Columbus  and 
implored  his  intercession.  They  promised  to  let  him  want 

171 


ECLIPSES   AND  TRANSITS 

for  nothing  if  only  he  would  avert  this  judgment.  As  an 
earnest  of  their  sincerity,  they  collected  hastily  a  quantity  of 
food  and  offered  it  at  his  feet.  At  first,  diplomatically  hesi- 
tating, Columbus  presently  affected  to  be  softened  by  their 
entreaties.  He  consented  to  intercede  for  them  ;  and  retiring 
to  his  cabin,  performed,  as  they  supposed,  some  mystic  rite 
which  should  deliver  them  from  the  threatened  punishment. 
Soon  the  terrible  shadow  passed  away  from  the  face  of  the 
Moon,  and  the  gratitude  of  the  savages  was  as  deep  as  their 
previous  terror ;  and  henceforth  there  was  no  failure  in  the 
regular  supply  of  provisions  to  the  castaways." 

It  is  well  to  bear  in  mind  the  differences  between  the 
two  kinds  of  eclipses.  While  a  lunar  eclipse  may  last 
for  several  hours,  a  solar  eclipse  is  a  matter  of  a  few 
minutes ;  and  while  a  lunar  eclipse  can  only  take  place 
at  full  Moon,  a  solar  eclipse  occurs  at  new  Moon. 
Professor  Gregory  gives  an  instance  of  a  'novelist  who, 
in  one  of  his  books,  describes  an  eclipse  of  the  sun 
which  took  place  at  full  Moon  and  lasted  half-an-hour  ! 
A  little  knowledge  of  the  theory  of  eclipses  would  pre- 
vent such  an  error.  As  has  been  pointed  out,  an  eclipse 
of  the  Moon  is  caused  by  the  immersion  of  our  satellite 
in  the  shadow  of  the  Earth.  A  solar  eclipse,  on  the 
other  hand,  is  caused  by  the  Moon's  shadow  falling  on 
our  planet.  The  Moon  is  a  much  smaller  body  than 
the  Earth,  and  consequently  it  has  a  much  smaller 
shadow.  The  shadow  is  too  small  to  completely  cover 
the  Earth.  It  merely  falls  on  a  portion  of  the  globe 
and  at  the  parts  immersed  in  the  shadow  the  Sun  is 
totally  eclipsed.  Solar  eclipses  last  only  a  few  minutes ; 
and  they  are  confined  to  a  narrow  strip  known  as  the 
shadow  track.  At  any  given  place  on  the  Earth's 
surface,  total  eclipses  of  the  Sun  are  rare.  There  has 
not  been  a  total  eclipse  of  the  Sun  visible  in  the 
United  Kingdom  since  1724,  and  there  will  not  be 

172 


ECLIPSE  OF  THE  SUN 

The  total  solar  eclipse  of  1900,  visible  in  Spain  and  Portugal.  The  black  disc  of 
the  moon  hides  the  glowing  fire  of  the  orb  of  day,  and  so  allows  us  to  see  the 
brilliant  prominences  and  the  mystic,  silvery  corona. 


ECLIPSES  AND   TRANSITS 

another  till  1927.  However,  though  rare  at  given  points 
on  the  surface  of  our  planet,  they  are  fairly  frequent  when 
the  Earth  is  considered  as  a  whole.  There  are  three  kinds 
of  solar  eclipses — total,  partial,  and  annular.  A  total  eclipse 
takes  place  when  the  Moon  is  at  its  nearest  point  to  the 
Earth,  and  consequently  appears  just  large  enough  to  hide 
the  Sun,  and  when  our  satellite  is  exactly  in  a  line  with 
the  Earth  and  Sun.  A  partial  eclipse  occurs  when  the 
Moon  is  not  exactly  in  a  line  with  the  Earth  and  Sun, 
and  only  covers  a  portion  of  the  disc ;  while  an  annular 
eclipse  takes  place  when  the  Moon  is  at  its  farthest  point 
from  the  Earth,  and  does  not  appear  to  be  large  enough 
to  cover  the  disc  of  the  Sun,  and  thus  we  see  an  "  annulus  " 
or  ring  of  light  round  the  Moon's  disc.  Of  these  three 
classes,  only  total  eclipses  are  useful  to  astronomers,  and 
that  only  because  of  a  peculiar  combination  of  circum- 
stances. Seen  from  the  Earth,  the  Sun  and  Moon  appear 
to  be  about  the  same  size.  Consequently,  at  a  total 
eclipse  the  Moon  is  large  enough  to  cover  the  large  and 
glowing  disc  of  the  Sun,  but  not  large  enough,  fortunately 
for  the  science  of  astronomy,  to  obscure  the  immediate 
surroundings  of  the  orb  of  day. 

When  a  solar  eclipse  takes  place,  expeditions  are  sent  to 
observe  the  phenomena  from  all  parts  of  the  globe.  Those 
who  are  unacquainted  with  the  problems  of  solar  astro- 
nomy may  think  it  strange  that  so  many  expeditions  are 
despatched  to  observe  the  obscuration  of  the  Sun  by  the 
Moon,  an  event  in  itself  of  no  particular  importance.  But 
owing  to  a  combination  of  circumstances  these  obscura- 
tions have  proved  to  be  full  of  interest  to  the  astro- 
nomer.  The  interposition  of  the  Moon  enables  us  to 
study  the  fainter  and  outlying  portions  of  the  Sun.  In 
the  words  of  Professor  Campbell,  the  director  of  the  Lick 

173 


ECLIPSES   AND  TRANSITS 

Observatory  :  "  Our  Sun  is  one  of  the  ordinary  stars.  In 
size  perhaps  it  is  only  an  average  star,  or  it  may  be  below 
the  average.  It  is  the  only  star  near  enough  to  us  to  show 
a  disc.  All  other  stars  are  as  mathematical  points,  even 
when  our  greatest  telescopes  magnify  them  three  thousand 
fold.  The  point  image  of  a  distant  star  includes  all  its 
details,  and  it  must  be  studied  as  a  whole,  whereas  the 
Sun  can  be  studied  in  geometrical  detail.  It  is  not  too 
much  to  say  that  our  physical  knowledge  of  the  stars 
would  be  practically  a  blank  if  we  had  been  unable  to 
approach  it  through  the  study  of  our  Sun.  If  we  would 


EarlH 


FIG.  7.— Total  and  Partial  Eclipses  of  the  Moon.  The  Moon  is 
here  shown  in  two  positions:  i.e.  entirely  plunged  in  the 
Earth's  shadow  and  therefore  totally  eclipsed,  and  only  partly 
plunged  in  it  or  partially  eclipsed. 

understand  the  other  stars,  we  must  first  make  a  complete 
study  of  our  own  star.  Several  of  the  most  interesting 
portions  of  our  Sun  are  invisible  except  at  times  of  solar 
eclipse.  Our  knowledge  of  the  Sun  will  be  incomplete 
until  these  portions  are  thoroughly  understood ;  and  this 
is  the  reason  why  eclipse  expeditions  are  despatched,  at 
great  expense  of  time  and  money,  to  occupy  stations 
within  the  narrow  shadow  belts.11 

The  chief  objects  of  study  during  total  eclipses  are  the 
solar  prominences  and  the  reversing  layer — or  shallow  solar 

174 


ECLIPSES  AND  TRANSITS 

atmosphere — and  the  corona.  The  red  prominences  were 
formerly  observable  only  during  total  eclipse,  but  in  1868 
M.  Janssen,  viewing  the  total  eclipse  in  India,  and  Sir 
Norman  Lockyer,  reasoning  the  matter  out  in  England, 
discovered  the  method  by  which  prominences  could  be 
observed  in  full  sunlight,  by  means  of  the  spectroscope. 
Accordingly,  less  attention  is  devoted  to  them  during  total 
eclipses.  It  may,  however,  be  remarked  that  a  class  of 
objects  known  as  "  white  "  prominences,  discovered  by  the 
late  Professer  Tacchini  during  the  eclipse  of  1883,  are  ob- 
servable only  on  the  occasion  of  a  total  eclipse.  The  corona 
is  perhaps  the  chief  object  of  interest  in  eclipse  observations. 
The  corona  is  a  halo  of  light  which  makes  its  appearance 
as  soon  as  the  Sun  is  totally  eclipsed,  and  remains  in  view 
only  during  the  few  minutes  of  totality.  It  is  not  a  solar 
atmosphere,  using  that  word  in  its  proper  sense,  and  it  is 
probably  of  a  compound  nature.  The  spectroscope  has 
had  little  chance  to  teach  us  much  regarding  the  corona, 
owing  to  the  faintness  of  the  spectrum,  and  the  short 
time  of  visibility.  Professor  Young  considers  that  the 
coronal  spectrum  is  composed  of  four  superposed  spectra — 
indicating,  of  course,  that  the  corona  is  a  compound  pheno- 
menon. First,  there  is  the  continuous  spectrum  due  pro- 
bably to  incandescent  dust,  or  solid  and  liquid  particles 
near  the  Sun ;  secondly,  the  gaseous  spectrum,  indicating 
the  presence  of  gases  of  a  permanent  nature.  This 
spectrum  is  distinguished  by  a  green  line,  which  has  not 
been  identified  with  any  terrestrial  element.  Thirdly, 
there  is  the  continuous  spectrum  of  reflected  sunlight 
with  the  dark  Fraunhofer  lines,  due  to  sunlight  reflected 
»from  meteoric  dust ;  and  fourthly,  the  light  reflected  in 
the  Earth's  atmosphere.  Drawings  and  photographs  of 
the  corona  show  that  its  size  and  shape  vary  in  a 

175 


ECLIPSES  AND  TRANSITS 

period  of  eleven  years,  corresponding  with  the  changes  of 
the  solar  spots,  and  even  more  nearly  so  with  the  period 
of  the  prominences.  In  fact,  the  late  Professor  Tacchini 
showed  that  the  distribution  of  the  prominences  and  the 
shape  of  the  corona  vary  in  harmony.  There  is  still  much 
uncertainty  as  to  the  actual  nature  of  the  corona,  and  as 
to  what  part  electricity  and  magnetism  may  play  in  the 
phenomenon.  In  Professor  Campbell's  words  :  "  Much 
has  been  written  concerning  a  possible  eruptive  origin  or 
about  magnetic  influences  in  shaping  the  forms  of  its 
streamers.  ...  It  is  a  surprising  fact  that,  with  all  the 
changes  of  form,  we  do  not  know  whether  the  materials 


ftonn 


FIG.  8. — Total  Eclipse  of  the  Sun.  From  the  position  A  the  Sun 
cannot  be  seen,  and  it  is  entirely  blotted  out  by  the  Moon. 
From  B  it  is  seen  partially  blotted  out,  because  the  Moon 
is  to  a  certain  degree  in  the  way.  From  C  no  eclipse  is  seen, 
because  the  Moon  does  not  come  in  the  way. 

composing  the  streamers  are  moving  in  or  out,  or  both  or 
neither.  .  .  .  Photographs  of  the  corona  should  be  secured 
for  this  purpose  at  widely  separated  stations — preferably 
at  three  or  more  stations — with  essentially  identical  in- 
struments and  with  equivalent  exposures,  in  order  that 
results  may  be  as  nearly  comparable  as  possible." 

The  reversing  layer  of  the  Sun  was  discovered  by  Pro- 
fessor Young  by  means  of  the  spectroscope,  during  the 
total  eclipse  of  1870,  visible  in  Spain.  As  the  solar 
crescent  grew  thinner,  says  Professor  Young,  "  the  dark 
lines  of  the  spectrum  itself  gradually  faded  away,  until  all 

176 


ECLIPSES  AND  TRANSITS 

at  once,  as  suddenly  as  a  bursting  rocket  shoots  out  its 
stars,  the  whole  field  of  view  was  filled  with  bright  lines 
more  numerous  than  one  could  count.  The  phenomenon 
was  so  sudden,  so  unexpected,  and  so  wonderfully  beauti- 
ful as  to  force  an  involuntary  exclamation."  Professor 
Young  concluded  that  every  line  in  the  spectrum  had 
become  bright,  and  hence  the  newly-disclosed  layer  of  the 
Sun  was  called  the  "  reversing  layer."  In  1896  its  spectrum 
was  photographed  by  an  English  observer. 

The  eclipse  problem  which  appeals  most  to  the  popular 
mind  is  perhaps  that  of  the  possible  existence  of  intra- 
Mercurial  planets,  already  discussed  in  an  earlier  chapter. 
With  the  exception  of  some  doubtful  observations  in  1878, 
eclipse  observations  have  tended  to  negative  the  idea  of 
even  a  small  planet  within  the  orbit  of  Mercury.  Photo- 
graphs were  secured  by  Mr.  W.  H.  Pickering  in  1900, 
and  by  Professor  Perrine  in  1901,  and  on  these  no 
trace  of  an  intra-Mercurial  planet  was  seen.  Professor 
Campbell  made  an  exhaustive  search  during  the  total 
eclipse  of  August  30,  1905,  visible  in  Spain,  and  no  trace 
of  an  intra-Mercurial  planet  could  be  found. 

For  those  who  have  never  seen  a  total  eclipse,  the 
following  description  by  an  American  writer,  Mrs.  Todd, 
is  worth  reading  as  illustrating  the  magnificence  of  the 
spectacle :  "  With  frightful  velocity  the  actual  shadow  of 
the  Moon  is  often  seen  approaching,  a  tangible  darkness 
advancing  almost  like  a  wall,  swift  as  imagination,  silent 
as  doom.  The  immensity  of  Nature  never  comes  quite  so 
near  as  then,  and  strong  must  be  the  nerve  not  to  quiver 
as  this  blue-black  shadow  rushes  upon  the  spectator  with 
incredible  speed.  .  .  .  Sometimes  the  shadow  engulfs 
the  observers  smoothly,  sometimes  apparently  with  jerks ; 
but  all  the  world  might  well  be  dead  and  cold  and  turned 

177  M 


ECLIPSES   AND   TRANSITS 

to  ashes.  Often  the  very  air  seems  to  hold  its  breath  for 
sympathy ;  at  other  times  a  lull  suddenly  awakens  into  a 
strange  wind,  blowing  with  unnatural  effect.  Then  out 
upon  the  darkness,  gruesome  but  sublime,  flashes  the  glory 
of  the  incomparable  corona,  a  silvery,  soft,  unearthly  light, 
with  radiant  streamers,  stretching  at  times  millions  of 
uncomprehended  miles  into  space,  while  the  rosy  flaming 
protuberances  skirt  the  black  rim  of  the  Moon  in  ethereal 
splendour.  It  becomes  curiously  cold,  dew  frequently 
falls,  and  the  chill  is  frequently  mental  as  well  as  physical. 
Suddenly,  instantaneous  as  a  lightning  flash,  an  arrow  of 
actual  sunlight  strikes  the  landscape,  and  Earth  comes  to 
life  again,  while  corona  and  protuberance  melt  into  the 
returning  brilliance." 

For  many  years  eclipses  both  of  the  Sun  and  the  Moon 
were  a  source  of  terror  to  mankind  before  proper  know- 
ledge had  been  gained  of  their  true  cause.  And  even 
to-day  in  uncivilised  nations  eclipses  cause  much  con- 
sternation. In  China,  drums  are  beat  and  trumpets  blown 
to  frighten  the  "  dragon  "  which  is  supposed  to  be  devour- 
ing the  Sun.  The  Hindus  think  that  an  eclipse  causes 
food  to  be  unclean,  and  consequently  that  it  is  unfit  for 
use.  The  following  cutting  from  an  American  newspaper 
in  1878  indicates  the  excitement  caused  among  the  Red 
Indians  by  the  total  solar  eclipse  of  29th  July  1878  : 
"  Some  of  them  threw  themselves  upon  their  knees,  others 
flung  themselves  flat  on  the  ground,  face  downwards ; 
others  cried  and  yelled  in  frantic  excitement  and  terror. 
At  last  an  old  Indian  stepped  from  the  door  of  his  lodge, 
pistol  in  hand,  and,  fixing  his  eyes  on  the  darkened  sun, 
mumbled  a  few  unintelligible  words,  and,  raising  his  arm, 
took  direct  aim  at  the  luminary,  fired  off  his  pistol,  and 
after  throwing  his  arms  about  his  head,  retreated  to  his 

178 


ECLIPSES   AND  TRANSITS 

own  quarters.  As  it  happened,  that  very  instant  was  the 
conclusion  of  totality.  The  Indians  beheld  the  glorious 
orb  of  day  once  more  peep  forth,  and  it  was  unanimously 
voted  that  the  timely  discharge  of  the  pistol  was  the 
only  thing  that  drove  away  the  shadow,  and  saved  them 
from  the  public  inconvenience  that  would  certainly  have 
resulted  from  the  entire  extinction  of  the  Sun." 

Closely  allied  to  eclipses  are  transits.  Only  two  planets 
can  be  seen  in  transit  across  the  Sun — Mercury  and  Venus. 
These  transits  occur  like  eclipses  of  the  Sun,  when  the 
Sun,  the  Earth,  and  Mercury,  or  the  Sun,  the  Earth, 
and  Venus,  are  in  a  straight  line.  But  owing  to  the  very 
small  apparent  size  of  Mercury  and  Venus,  as  seen  from 
the  Earth,  there  is  no  eclipse.  We  merely  see  the  black 
discs  of  the  planets  as  spots  on  the  glowing  face  of  the 
Sun.  The  first  observed  transit  of  Venus  was  predicted 
by  Kepler  for  1631.  These  transits  take  place  in  pairs, 
separated  by  intervals  of  eight  years,  and  the  pairs  are 
separated  by  intervals  of  105J  and  121^  years.  Kepler, 
although  he  had  predicted  the  transit  of  1631,  was  un- 
aware of  the  fact  that  transits  occur  in  pairs,  and  he  did 
not  expect  another  until  1761.  A  transit,  however,  took 
place  in  1-639,  and  was  only  witnessed  by  two  persons. 
The  story  of  its  observation  is  an  interesting  one,  and  has 
long  been  a  favourite  among  lovers  of  astronomy. 

A  young  Englishman,  Jeremiah  Horrocks,  a  curate  in  the 
English  Church,  became  at  a  very  early  age  proficient  in 
mathematical  astronomy,  and  ascertained  the  fact  that  a 
transit  of  Venus,  which  Kepler  had  overlooked,  would  take 
place  in  1639.  The  day  he  predicted  for  the  transit 
happened  to  be  a  Sunday,  and  Horrocks  could  not  observe 
continuously  owing  to  his  duties  as  a  clergyman.  At  nine 
o'clock  he  was  obliged  to  suspend  observations,  but  at  ten 

179 


ECLIPSES  AND   TRANSITS 

he  was  again  watching.  He  saw  nothing  on  the  Sun's  disc. 
At  noon  he  was  again  at  church,  but  by  one  o'clock  he  was 
enabled  to  resume  observations.  To  his  sorrow,  the  sky 
clouded,  and  he  almost  abandoned  hope  of  seeing  the  event 
he  had  predicted.  But  in  the  afternoon  the  clouds  dis- 
persed ;  the  orb  of  day  shone  out  once  more,  and  the  young 
astronomer  beheld,  to  his  intense  delight,  Venus  in  transit 
across  the  Sun.  He  had  informed  only  one  man,  his  young 
friend  William  Crabtree,  of  the  occurrence  of  the  event,  and 
Crabtree  also  succeeded  in  observing  the  transit ;  but  these 
two  young  men  were  the  only  observers  of  this  occurrence, 
unexpected  by  the  astronomers  of  the  day.  Horrocks,  who 
gave  promise  of  becoming  one  of  the  greatest  astronomers 
of  his  time,  did  not  long  survive  his  triumph.  He  died 
shortly  after  at  the  early  age  of  twenty-two. 

The  next  pair  of  transits  occurred  in  1761  and  1769. 
Before  they  took  place,  however,  Halley  had  pointed  out 
that  observations  on  Venus  while  in  transit  would  lead  to 
a  correct  measurement  of  the  distance  of  the  Sun,  and  con- 
sequently several  expeditions  were  sent  to  observe  these 
transits  at  different  ends  of  the  Earth.  As  an  erroneous 
estimate  of  the  Sun's  distance  was  deduced  from  these 
measurements,  astronomers  looked  eagerly  forward  to  the 
next  two  transits  in  1874  and  1882.  As  before,  expeditions 
were  despatched  to  all  regions  of  the  globe,  but  the  results 
were  disappointing,  and  astronomers  have  since  devised 
better  and  more  accurate  methods  of  measuring  the  Sun's 
distance.  The  next  pair  of  transits  of  Venus  will  take  place 
in  2004  and  2012,  and  there  will  be  another  pair  in  2117 
and  2 1 25.  The  reason  of  the  rarity  of  these  occurrences 
is  the  fact  that  the  orbit  of  Venus  is  not  exactly  in  the  same 
plane  as  that  of  our  Earth. 

Transits  of  Mercury  are  not  of  so  much  interest  as  those 
180 


ECLIPSES   AND  TRANSITS 

of  Venus,  and  they  are  much  more  frequent.  The  last  took 
place  in  1907,  and  there  will  be  another  in  1917. 

Closely  allied  both  to  eclipses  and  transits  are  occul- 
tations.  The  difference,  however,  between  transits  and 
occultations  is  that,  while  a  transit  is  the  passage  of  an 
apparently  small  body  over  an  apparently  large  body,  an 
occultation  is  the  obscuration  of  a  body  apparently  small 
by  a  body  apparently  large.  Thus  when  the  Moon  passes 
over  Jupiter  or  Mars,  or  a  star,  it  is  said  to  occult  these 
objects. 

In  the  system  of  Jupiter,  which  we  only  observe  from  a 
considerable  distance,  we  can  observe  eclipses,  transits,  and 
occultations.  We  see  the  satellites  immersed  in  the  shadow, 
and  we  can  also  observe  them  in  transit  across  the  disc  of 
their  primary.  In  addition,  we  can  observe  Jupiter  passing 
over  and  occulting  these  small  bodies.  Thus  observation 
of  the  system  of  Jupiter  gives  us  a  practical  illustration  of 
the  fact  that  eclipses,  transits,  and  occultations  are  all 
kindred  phenomena,  arising  from  the  fact  that  every  body 
shining  by  reflected  light  casts  a  shadow  into  space. 


181 


CHAPTER   XVIII 

THE   SUNS   OF   SPACE 

WHEN  we  lift  our  eyes  to  the  heavens  on  any 
clear  moonless  night,  apparently  innumerable 
luminous  points  of  all  degrees  of  brightness  at- 
tract our  attention.  They  are  fixed  in  position  relatively 
to  one  another,  and  they  rise  and  set  like  the  Sun.  These 
are  the  stars — the  stars  proper,  as  distinguished  from  the 
planets  or  "  wandering  stars."  These  stars  are  the  same 
orbs  which  shone  down  on  Job,  and  Homer,  and  the  ancient 
writers  of  thousands  of  years  ago  ;  and  it  is  a  solemn 
thought  when  we  look  upward  to  the  star-spangled  heavens 
that  the  same  constellations  and  star  groups  met  the  gaze 
of  generations  upon  generations  which  have  long  since 
passed  away.  Homer  and  Hesiod  both  refer  to  the  con- 
stellations. Job  mentions  Orion  and  the  Pleiades,  and 
also,  it  is  believed,  the  Great  Bear.  This  fact  proves  that 
long  ago,  before  astronomy  was  founded  on  a  scientific 
basis,  the  early  star-gazers  had  already  divided  the  sky  into 
constellations,  and  had  given  to  them  names.  These  star- 
groups  are  recognised  by  astronomers  to-day,  and  one  of 
the  first  steps  for  the  beginner  in  astronomy  is  to  learn 
the  constellations.  Just  as  in  botany  and  geology  respec- 
tively, it  is  necessary  to  know  the  various  flowers  and  the 
different  classes  of  rocks  by  name,  so  in  astronomy  it  is 
essential  to  know  the  constellations,  and  to  be  able  to 
follow  them  throughout  the  changing  seasons. 

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THE   SUNS   OF  SPACE 

Most  people  are  familiar  with  the  Great  Bear  or  Ursa 
Major,  or  at  least  with  its  most  prominent  part,  the  Plough. 
The  Plough  is  not  the  most  conspicuous  constellation,  but 
it  is  visible  all  the  year  round,  and  its  shape  is  very  easily 
remembered.  But  its  position  varies  from  month  to  month. 
It  is  essential  to  remember  that  the  aspect  of  the  heavens 
changes  with  the  seasons.  Not  only  do  the  stars  appear 
to  go  round  the  Earth  once  in  twenty-four  hours,  but, 
owing  to  the  apparent  motion  of  the  Sun,  the  stars  appear 
to  rise  and  set  four  minutes  earlier  every  night.  The 
result  is  a  constant  change,  gradual  but  steady,  in  the 
position  of  the  stars  at  any  given  time,  and  at  the  end  of 
the  year  the  revolution  is  completed  and  the  stars  return 
to  the  places  which  they  occupied  a  year  before.  One  star 
in  the  heavens,  however,  scarcely  changes  its  position  at 
all.  This  is  a  fairly  bright  object  in  the  northern  sky, 
known  as  the  Pole  Star,  so  called  because  the  axis  of  the 
Earth  points  almost  exactly  to  it.  That  is  to  say,  were 
we  standing  exactly  at  the  North  Pole,  we  should  see  the 
Pole  Star  almost  exactly  overhead.  The  Pole  Star  there- 
fore remains  practically  fixed  in  position,  while  all  the  stars 
in  the  sky  appear  to  revolve  round  it.  The  farther  the 
star  from  ,the  Pole,  the  wider  the  circle  which  it  appears 
to  describe.  Thus,  the  stars  of  Ursa  Minor,  the  constella- 
tion in  which  the  Pole  Star  is  situated,  describe  smaller 
circles  than  the  stars  in  the  Plough.  But  even  the  stars 
in  the  Plough  describe  a  relatively  small  circle.  They  are 
never  below  the  horizon,  and  their  ceaseless  revolution 
round  the  Pole  is  an  index  of  the  changing  seasons.  For 
instance,  in  the  spring  evenings,  the  Plough  is  almost 
directly  overhead ;  in  summer  evenings  it  is  in  the  north- 
west ;  in  autumn  evenings  it  is  low  down  in  the  north,  in 
winter  evenings  in  the  north-east. 

183 


THE   SUNS   OF   SPACE 

On  the  opposite  side  of  the  Pole  from  the  Plough  is  the 
constellation  Cassiopeia.  It  is  shaped  like  the  letter  W. 
Between  Cassiopeia  and  the  Plough  is  Auriga,  a  star  group 
dominated  by  a  brilliant  star  known  as  Capella,  and  on 
the  other  side  of  the  Pole  from  Auriga  is  Lyra,  another 
star  group  also  dominated  by  a  bright  star  known  as  Vega. 
These  four  constellations  are  almost  always  visible,  though 
sometimes  Auriga  and  Lyra  are  lost  in  the  haze  of  the 
horizon.  In  England  these  two  stars  disappear  for  a 
certain  time  in  the  haze  of  the  horizon  ;  but  in  Scotland 
and  northern  latitudes  they  are  nearly  always  to  be  seen. 

These  four  constellations,  moving  around  the  Pole,  con- 
stitute what  has  been  well  named  "  the  great  star  clock  of 
the  north.11  As  Mr.  E.  W.  Maunder  has  said :  "  To  watch 
these  northern  constellations,  as  they  follow  each  other  in 
ceaseless  procession  round  the  Pole,  is  one  of  the  most 
impressive  spectacles  to  a  mind  capable  of  realising  the 
significance  of  what  is  seen.  We  are  spectators  of  the 
movement  of  one  of  Nature*^  machines,  the  vastness  of 
the  scale  of  which,  and  the  absolutely  perfect  smoothness 
and  regularity  of  whose  working,  so  utterly  dwarf  the 
mightiest  work  accomplished  by  man.11 

Once  a  knowledge  of  the  northern  heavens  has  been 
gained,  it  is  a  comparatively  easy  matter  to  learn  the  names 
and  outlines  of  the  remaining  constellations.  Each  season 
has  its  own  particular  groups.  For  instance,  Orion,  Taurus, 
and  Canis  Major  are  the  great  constellations  of  winter, 
even  though  they  may  be  seen  in  spring  and  autumn  ;  but 
it  is  in  winter  that  they  are  seen  to  most  advantage,  and 
that  they  are  visible  at  the  most  convenient  hours  of  the 
night.  Similarly  with  the  other  stars.  In  spring  we  have 
Leo,  Virgo,  and  Bootes  dominating  our  skies ;  in  summer 
we  have  Lyra,  Scorpio,  Hercules,  Corona  Borealis ;  in 

184 


THE   SUNS   OF   SPACE 

autumn  Cygnus,  Aquila,  Aries,  Perseus,  and  other  groups. 
As  the  seasons  advance,  the  reappearance  of  a  familiar 
constellation  lends  a  new  charm  and  interest  to  the  evening 
walk.  Not  only  the  constellations  themselves,  but  the 
stars  which  compose  them  have  their  own  designation. 
Some  of  the  brighter  stars,  such  as  Sirius,  Vega,  Arcturus, 
and  Capella  have  proper  names,  but  the  vast  majority  are 
designated  by  letters  of  the  Greek  alphabet.  Thus  the 
bright  star  Aldebaran  is  also  known  as  Alpha  Tauri,  Tauri 
being  the  genitive  of  the  Latin  noun  Taurus.  Similarly, 
Sirius  is  Alpha  Canis  Majoris.  When  the  Greek  letters  in 
each  constellation  are  exhausted,  numbers  are  used  also 
with  the  genitive  of  the  Latin  noun.  Thus  we  talk  of  61 
Cygni,  42  Comae  Berenices,  &c. 

So  much  for  the  stars  as  they  appear ;  but  the  science 
of  astronomy  enables  us  to  understand  what  the  stars 
really  are.  To  us  they  appear  little  twinkling  points  of 
light  suspended  above  the  clouds,  useful  on  a  moonless 
night.  Astronomy  teaches  us  that,  so  far  from  being 
merely  little  points  of  light,  the  stars  are  suns.  This  great 
truth  gradually  dawned  on  mankind.  Even  Copernicus 
had  very  hazy  notions  as  to  the  nature  of  the  stars.  But 
as  astronomy  developed,  and  as  better  instruments  were 
invented,  our  information  concerning  the  distant  orbs 
increased,  until  to-day  our  knowledge  of  the  stars  is 
considerable.  It  was  the  great  Sir  William  Herschel 
who  first  studied  the  stars  systematically ;  and  so  many 
and  important  were  his  discoveries,  and  so  great  was  the 
interest  in  the  stars  aroused  by  his  investigations,  that 
since  the  commencement  of  his  work  stellar  astronomy — 
as  distinguished  from  planetary  astronomy — has  gone 
from  triumph  to  triumph.  The  stars  are  suns.  This  is 
the  first  great  truth  which  we  must  bear  in  mind.  Very 

185 


THE   SUNS   OF   SPACE 

insignificant  they  seem,  even  the  brighter  objects  among 
them  being  almost  obliterated  by  the  moonlight,  utterly 
extinguished  by  the  sunlight,  and  seeming  very  small  and 
unimportant  beside  Jupiter,  Venus,  and  Mars.  As  we 
saw  in  preceding  chapters,  distance  is  often  very  deceptive. 
The  Moon,  for  instance,  shines  many  times  more  brightly 
than  Jupiter,  and  yet  it  belongs  to  an  altogether  inferior 
order  of  bodies.  It  is  only  a  satellite,  the  attendant  of 
our  world,  while  Jupiter  is  a  planet  many  times  larger  than 
the  Earth.  Jupiter  shines  many  times  more  brilliantly 
than  Sirius,  the  brightest  of  the  stars.  Yet  Jupiter  is  to 
the  stars  as  the  Moon  is  to  Jupiter ;  for  the  stars  are 
suns,  and  Jupiter  sinks  to  utter  insignificance  compared 
with  even  the  faintest  of  the  stars.  It  belongs  to  an 
altogether  inferior  order  of  bodies. 

It  is  the  vast  distance  of  the  stars  which  explains  their 
apparent  insignificance — a  distance  so  vast  that  for  many 
years  it  was  hopeless  to  attempt  to  measure  it.  In  a 
previous  chapter  explanation  was  made  of  the  principle 
of  measurement  of  the  celestial  distances  and  of  the 
meaning  of  the  term  "parallax."  If  the  measurement  of 
the  distances  of  the  Sun  and  planets  is  difficult,  it  will 
easily  be  understood  how  much  more  difficult  is  the 
measurement  of  the  distances  of  the  far-away  stars.  The 
fact  that  the  stars  showed  no  measurable  displacement 
greatly  perplexed  Copernicus.  It  was  argued — and  rightly 
—by  the  opponents  of  the  Copernican  system,  that  if  the 
Earth  had  an  annual  revolution  round  the  Sun,  there 
ought  to  be  a  corresponding  displacement  of  the  stars 
owing  to  the  observer's  change  of  position.  But  the  most 
careful  measurements  of  the  astronomers  of  that  day  failed 
to  show  any  displacement.  Copernicus  had  therefore  to 
claim  for  the  stars  a  much  greater  distance  than  he  was 

186 


THE   SUNS   OF   SPACE 

willing  to ;  for  in  those  days  men  had  a  very  inadequate 
idea  of  the  Universe.  Tycho  Brahe,  the  last  of  the  great 
pre-telescopic  astronomers,  also  attacked  the  question  and 
attempted  to  find  this  displacement,  but  he  failed.  After 
the  invention  of  the  telescope  many  attempts  were  made, 
but  in  vain.  The  greatest  astronomers  were  baffled,  among 
them  such  men  as  Bradley  and  Herschel ;  and  it  was  not 
until  the  third  decade  of  the  nineteenth  century  that  the 
first  milestone  of  Infinity,  so  to  speak,  was  reached. 

Three  attempts  were  made  independently  to  measure 
this  displacement.  In  1835  the  German  astronomer  Struve 
commenced  a  series  of  measurements  on  the  bright  star 
Vega,  but  the  distance  which  he  deduced  from  his 
measurements  proved  so  far  from  the  truth  that  the  result 
was  practically  useless.  Other  two  attempts  proved  more 
successful.  The  German  astronomer  Bessel  succeeded  in 
measuring  the  distance  of  a  faint  little  star  of  the  fifth 
magnitude  numbered  61  in  the  constellation  Cygnus. 
At  the  same  time  Thomas  Henderson,  the  great  Scottish 
astronomer,  afterwards  Astronomer  Royal  of  Scotland, 
measured  the  distance  of  what  has  proved  to  be  the 
nearest  star.  While  employed  as  the  Astronomer  Royal 
at  the  Cape  of  Good  Hope,  he  made  a  series  of  observa- 
tions on  the 'brilliant  star  known  as  Alpha  Centauri,  one 
of  the  brightest  stars  in  the  heavens,  and  he  succeeded  in 
measuring  its  distance.  This  distance  is  about  twenty- 
five  billions  of  miles.  Such  figures  are  unthinkable.  The 
entire  solar  system  is  about  five  thousand  millions  of 
miles  in  diameter — a  great  diameter,  it  is  true,  but  in- 
considerable when  compared  to  the  enormous  distance  of 
the  nearest  star.  Our  solar  system  is  indeed  a  little 
island  in  space,  a  mere  speck  in  the  greater  system  of  the 
stars.  It  is  difficult  to  obtain  a  true  idea  of  this  vast 

187 


THE   SUNS   OF   SPACE 

distance.  The  late  Dr.  Dolmage,  in  his  book  "  Astronomy 
of  To-Day,"  gives  an  unique  illustration  which  should 
help  the  reader  a  little,  as  it  were,  in  comprehending  the  in- 
comprehensibleness  of  this  distance  : — "  What  is  a  million  ? 
It  is  a  thousand  thousands.  But  what  is  a  billion  ?  It 
is  a  million  millions.  Consider  for  a  moment.  A  million 
of  millions.  That  means  a  million,  each  unit  of  which  is 
itself  a  million.  Here  is  a  way  of  trying  to  realise  this 
gigantic  number.  A  million  seconds  make  only  eleven 
and  a  half  days  and  nights.  But  a  billion  will  make 
actually  more  than  thirty  thousand  years."" 

An  idea  of  the  immense  distance  of  the  nearest  star 
may  be  gained  from  consideration  of  the  fact  that  if  the 
distance  from  the  Sun  to  Neptune  were  represented  by  ten 
feet,  Alpha  Centauri  would  be  fourteen  miles  away.  But 
the  true  method  by  which  we  can  properly  comprehend 
the  distances  of  the  stars  is  by  considering  the  velocity 
of  light.  Light  crosses  the  diameter  of  the  entire  solar 
system  in  eight  hours  ;  yet  it  takes  about  four  years  to 
span  the  gulf  which  separates  our  system  from  the  nearest 
star.  What,  then,  of  the  more  distant  stars  ?  61  Cygni 
is  about  fifty-three  billions  of  miles  away,  and  light 
requires  about  seven  years  to  reach  us  from  that  orb. 
Sirius,  the  most  brilliant  star  in  the  sky,  is  distant  fifty- 
eight  billions  of  miles,  and  light  is  eight  years  on  the 
journey. 

In  the  vast  majority  of  cases  there  is  no  visible  dis- 
placement of  the  stars  in  the  sky,  and  their  distances 
cannot  be  measured.  An  idea  of  the  great  difficulty  of 
measuring  this  parallax  or  displacement  may  be  gathered 
from  the  remark  of  an  American  writer,  Mr.  G.  P.  Serviss, 
that  the  displacement  "  is  about  equal  to  the  apparent  dis- 
tance between  the  heads  of  two  pins  placed  an  inch  apart  and 

188 


THE  SUNS  OF  SPACE 

viewed  from  a  distance  of  180  miles.11  The  wonder  is  not 
that  astronomers  have  measured  the  distance  of  so  few 
stars,  but  that  they  have  succeeded  in  measuring  the  dis- 
tances of  any.  Comparatively  few  distances  have  been 
measured  with  any  approach  to  accuracy.  A  number 
have  been  measured  roughly  and  a  number  estimated.  It 
might  be  supposed  that  the  brightest  stars,  those  of  the 
first  magnitude,  are  nearest  to  the  Earth  ;  but  such  is  not 
the  case.  Sirius,  it  is  true,  is  among  the  nearer  stars, 
but  it  is  at  a  greater  distance  than  61  Cygni,  an  insig- 
nificant little  star  of  the  fifth  magnitude.  Thus  we  see 
that,  just  as  there  are  great  diversities  among  the  planets, 
so  the  stars  are  far  from  being  all  of  the  same  size.  A 
tolerably  accurate  measurement  of  the  distance  of  the 
brilliant  star  Arcturus  has  been  made.  So  vast  is  the  dis- 
tance, that  light  takes  over  two  hundred  years  to  travel  to  our 
system  from  its  glowing  surface.  How  enormous  therefore 
must  be  the  star  which  shines  so  brilliantly  from  so  vast  a 
distance.  The  diameter  of  Arcturus  is  believed  to  be  about 
sixty-two  millions  of  miles.  Compared  with  Arcturus,  our 
Sun,  great  and  splendid  orb  as  he  seems  to  us,  is  a  puny 
dwarf.  Mr.  Garret  P.  Serviss  says  of  this  enormous  sun  : 
"  Imagine  the  Earth  and  other  planets  constituting  the 
solar  system  removed  to  Arcturus  and  set  revolving  round 
it  in  orbits  of  the  same  forms  and  sizes  as  those  in  which 
they  circle  about  the  Sun.  Poor  Mercury !  For  that 
little  planet  it  would  indeed  be  a  jump  from  the  frying- 
pan  into  the  fire,  because  as  it  rushed  to  perihelion,  the 
point  of  its  orbit  nearest  the  Sun,  Mercury  would  plunge 
more  than  2,500,000  miles  beneath  the  surface  of  the 
'giant  star.  Venus  and  the  Earth  would  melt  like  snow- 
flakes  at  the  mouth  of  a  furnace.  Even  far-away  Neptune 
would  swelter  in  torrid  heat."  Another  enormous  sun  is 

189 


THE   SUNS   OF   SPACE 

Rigel,  one  of  the  two  brilliant  orbs  in  Orion.  So  distant 
is  this  body  that  Sir  David  Gill  utterly  failed  to  measure 
its  distance.  Capella,  in  Auriga,  is  yet  another  gigantic 
orb.  According  to  Mr.  Gore,  it  is  about  fourteen  millions 
of  miles  in  diameter,  and  is  equal  in  volume  to  four  thousand 
suns  such  as  ours.  A  little  reflection  on  these  enormous 
sizes  shows  us  that  everything  in  the  Universe  is  relative. 
To  us  on  Earth  a  range  of  mountains  is  gigantic ;  the 
Earth  itself  is  so  vast  that  we  cannot  conceive  of  it  as  a 
globe  at  all,  and  we  can  only  regard  a  portion  of  it  at  a 
time.  And  what  of  the  Sun  ?  To  us  its  size  is  over- 
whelming. We  cannot  realise  a  diameter  a  hundred  times 
that  of  our  Earth.  And  as  to  the  stars,  we  may  repeat 
the  figures  which  denote  their  diameters,  but  we  cannot 
grasp  what  these  figures  mean.  The  stars  themselves  are 
of  all  sizes  and  at  all  distances.  All  are  enormously 
distant,  but  some  are  much  nearer  than  others.  All  are 
enormously  large,  but  some  much  larger  than  others.  Of 
the  two  thousand  visible  at  a  time  to  the  unaided  eye,  we 
have  measured  the  distances  of  very  few,  and  have  calcu- 
lated the  sizes  of  the  merest  handful.  And  yet  at  the 
very  beginning  of  our  investigations  among  the  suns  of 
space,  we  learn  that  indeed,  "  One  star  differeth  from 
another  star  in  glory/' 


190 


CHAPTER  XIX 
THE   REVELATIONS   OF   STARLIGHT 

WHEN  we  cast  an  upward  glance  to  the  heavens 
and  look  at  the  stars,  we  little  realise  what 
may  be  called  the  revelations  of  starlight ;  we 
little  imagine  that  in  the  rays  of  the  stars  are  borne  to  us 
most  of  the  secrets  of  the  Universe,  and  that  the  light  rays 
from  Immensity  tell  us  a  story  which  for  wonder,  mystery, 
and  majesty  is  unrivalled  in  the  realms  of  the  imagination. 
In  the  chapter  on  the  Sun,  reference  was  made  to  the 
spectroscopic  method  of  observing  that  luminary,  and  to 
the  knowledge  which  has  been  gained  from  a  study  of  the 
band  of  coloured  light  known  as  the  solar  spectrum.  It 
is  much  more  difficult  to  observe  the  spectra  of  the  various 
stars  than  the  spectrum  of  the  Sun,  owing  to  the  relative 
feebleness  of  starlight.  However,  since  1863  astronomers 
have  made  rapid  progress  in  this  branch  of  knowledge.  In 
that  year  the  late  Sir  William  Huggins  commenced  his  work 
in  this  department,  by  a  particular  study  of  two  stars  of  the 
first  magnitude,  Betelgeux  and  Aldebaran.  In  the  former 
star  he  ascertained  the  existence  of  the  elements  sodium, 
iron,  calcium,  magnesium,  and  bismuth,  and  in  the  latter 
the  same  elements,  with  the  addition  of  tellurium,  anti- 
mony, and  mercury.  Thus,  for  the  first  time,  the  rays  of 
starlight  had  revealed  to  humanity  the  constitution  of  the 
suns  of  space. 

Secchi,  a  well-known  Italian  astronomer,  made  a  classifi- 

191 


THE  REVELATIONS  OF  STARLIGHT 

cation  of  the  stars  in  the  heavens  about  the  same  time 
that  Sir  William  Huggins  started  his  observations.  It 
was  known  many  years  before  that  just  as  the  Sun  had 
a  different  spectrum  from  any  of  the  stars,  so  the  stars 
differed  among  themselves.  It  was  shown,  however,  by 
Secchi  that  the  stars  could  be  divided  into  four  well- 
defined  groups — white  stars,  yellow  stars,  red  stars,  and 
dark-red  stars,  according  to  the  variations  in  their  spectra. 
Although  other  more  scientific  classifications  have  since 
been  proposed  and  adopted,  the  first  classification  gives 
us  a  general  idea  of  the  different  types  of  stars.  When 
we  turn  our  eyes  to  the  heavens,  we  see  that  the  stars  are 
not  all  of  the  same  colour.  We  at  once  note  the  bluish 
white  of  Sirius,  the  red  colour  of  Betelgeux,  the  orange- 
red  hue  of  Aldebaran.  When  we  consider  the  bright 
stars  according  to  their  spectra,  we  find  that  Sirius,  Vega, 
Rigel,  Altair,  Regulus  are  included  in  the  class  known  as 
the  white  stars  or  the  Sirian  stars,  from  their  brightest 
example.  In  the  second  type  are  included  Capella, 
Arcturus,  Aldebaran,  Procyon,  Pollux,  and  the  Pole  Star. 
The  spectrum  of  our  Sun,  in  fact,  is  of  this  type,  and 
hence  this  class  of  orbs  is  known  as  the  group  of  solar  or 
yellow  stars.  The  stars  of  the  third  type  are  much  less 
numerous.  Betelgeux  and  Antares  are  the  most  notable 
representatives  of  this  type.  The  fourth  type  includes 
stars  of  a  deeper  red,  none  of  which  are  bright  enough  to 
command  the  attention  of  the  casual  observer.  The  first 
type  has  been  sub-divided  by  the  late  Dr.  Vogel  into  two 
sub-classes,  the  Orion  type  and  the  Sirian  type.  The 
stars  of  the  Orion  type  are  so  called  because  most  of  the 
stars  in  the  constellation  Orion  are  of  that  class.  They 
are  distinguished  by  the  presence  in  their  atmospheres 
of  the  element  helium.  Rigel,  in  Orion,  is  one  of  the 

192 


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THE   REVELATIONS   OF  STARLIGHT 

typical  stars  of  this  group,  and  a  massive  and  gigantic 
orb  it  appears  to  be.  Its  mass  is  no  less  than  34,000 
times  that  of  the  Sun,  the  enormous  orb  whose  size 
overwhelms  the  minds  of  mortals.  Rigel,  however,  as 
the  late  Miss  Clerke  pointed  out,  "  is  not  massive  in  the 
proportion  of  its  luminosity. "  It  gives  about  eight 
thousand  times  more  light  than  our  Sun,  "  but  the  Sun 
is  dimmed  to  about  one-third  of  its  native  lustre  by 
effects  of  absorption  which  are  virtually  absent  from  the 
star.  Hence  a  total  light  emission  8000  times  greater 
would  represent  a  radiating  surface  only  2667  times  more 
expansive  than  the  solar  photosphere.  Stars  of  the 
helium  variety  are  composed  of  highly  rarefied  materials." 

Sirius  and  Vega  may  be  taken  as  typical  stars  of  the 
second  sub-division  of  stars  of  the  first  type.  Stars  of 
the  solar  type  are  of  various  sizes.  Alpha  Centauri,  one 
of  our  nearer  neighbours  in  space,  seems  to  be  a  sun  in 
many  respects  similar  to  our  own.  Another  star  of  the 
solar  type  which  deserves  mention  is  Arcturus,  or  Alpha, 
of  the  constellation  Bootes.  Its  spectrum  is  of  the  solar 
type,  but  so  far  as  size  is  concerned,  as  mentioned  in 
the  last  chapter,  it  dwarfs  the  Sun  to  utter  insignificance, 
and  apparently  belongs  to  a  higher  order  of  suns  than 
the  ruler  of  our  own  planetary  system. 

In  a  work  like  the  present  it  is  obviously  impossible 
to  present  the  technical  details  of  the  researches  of 
astronomers  on  the  spectra  of  the  stars.  One  interesting 
discovery  may  be  mentioned.  It  might  be  supposed  that 
stars  of  the  different  types  are  scattered  over  the  sky  at 
> random,  but  such  is  not  the  case.  The  white  stars  congre- 
gate on  the  whole  in  a  definite  region  of  the  heavens,  that 
marked  by  the  Milky  Way  or  Galaxy  ;  while  the  solar  stars 
are  on  the  whole  distributed  with  some  approach  to  uni- 

193  N 


THE   REVELATIONS   OF   STARLIGHT 

formity.  The  meaning  of  this  difference  in  distribution 
of  the  two  types  will  be  unfolded  in  a  later  chapter. 

Although  most  of  our  knowledge  of  starlight  is  due  to 
the  marvellous  revelations  of  the  spectroscope,  a  consider- 
able amount  of  knowledge  has  been  gained  from  a  study 
of  starlight  by  the  telescope,  and  indeed  by  the  unaided 
eye.  Perhaps  the  most  remarkable  objects  in  the  heavens 
are  the  new  or  temporary  stars — orbs  which  blaze  out  in 
the  sky  where  no  previous  stars  have  been  seen,  and  which 
then  sink  into  invisibility.  Many  instances  of  temporary 
stars  have  been  recorded.  A  temporary  star  is  believed 
to  have  appeared  in  the  year  134  B.C.,  and  to  have  sug- 
gested to  Hipparchus,  the  famous  Greek  astronomer,  the 
idea  of  forming  a  catalogue  of  stars.  The  first  temporary 
star,  however,  of  which  we  have  any  authentic  record  was 
observed  by  Tycho  Brahe,  and  is  always  known  as  Tycho's 
Star.  The  famous  Danish  astronomer  was  not,  however, 
the  discoverer  of  the  star.  It  was  detected  by  a  German 
at  Wittenberg  on  August  6,  1572,  whereas  Tycho  did 
not  notice  it  until  November  11.  Looking  up  to  the  sky 
one  evening,  Tycho  was  astounded  to  see  the  appearance  of 
the  well-known  constellation  Cassiopeia  entirely  changed 
by  the  appearance  of  a  new  and  brilliant  star,  far  out- 
shining the  other  stars  of  the  group.  When  first  seen  by 
Tycho  Brahe,  the  new  star  was  brighter  than  Jupiter,  and 
when  it  reached  its  greatest  visibility  it  was  fully  equal 
to  Venus.  So  bright,  indeed,  was  the  new  star  that  in  a 
clear  sky  it  was  visible  in  full  daylight.  In  March  1574 
it  ceased  to  be  visible  to  the  unaided  eye. 

Another  bright  star,  usually  associated  with  the  name 
of  Kepler,  appeared  in  1604.  On  10th  October  of  that 
year,  one  of  Kepler's  pupils  noticed  that  a  new  and 
brilliant  star  had  made  its  appearance  in  the  constellation 

194 


THE  REVELATIONS  OF  STARLIGHT 

Ophinchus.  The  planets  Mars,  Jupiter,  and  Saturn  were 
close  together  in  the  same  constellation,  and  it  was  easy  to 
make  comparisons  between  the  new  star  and  the  planets. 
It  was  estimated  as  brighter  than  Mars  and  Jupiter,  and 
indeed  as  equal  to  Venus.  The  star,  which  was  also 
studied  by  Galileo,  disappeared  in  March  1606,  having 
been  visible  for  about  seventeen  months. 

These  two  stars  were  the  brightest  temporary  stars 
recorded  in  history.  The  next  authentic  instance  of  a 
similar  object  was  the  appearance  of  a  much  less  im- 
posing stellar  phenomenon.  By  the  middle  of  the  nine- 
teenth century  the  discovery  of  temporary  stars  was  a 
much  easier  matter  than  at  the  time  of  Galileo,  owing  to 
the  increased  power  of  telescopes  as  well  as  the  increased 
number  of  astronomers.  The  star  detected  by  the  Eng- 
lish observer  Hind,  on  April  28,  1848,  never  exceeded 
the  fifth  magnitude  in  brilliancy.  More  striking  was  the 
star  of  1866,  popularly  known  as  "  blaze  star.11  John 
Birmingham,  an  amateur  astronomer  at  Tuam,  in  Ireland, 
observing  the  heavens  with  the  unaided  eye  on  the 
evening  of  May  12,  1866,  detected  a  brilliant  star  in  the 
constellation  Corona  Borealis.  It  was  then  of  the  second 
magnitude,  and  equal  in  brilliance  to  the  brightest  star 
of  the  constellation.  It  must  have  increased  very  rapidly, 
for  Schmidt,  of  Athens,  one  of  the  most  competent  ob- 
servers of  the  day,  affirmed  that  when  he  scanned  the 
same  part  of  the  sky  four  hours  earlier  it  was  not  then 
visible,  although  he  was  sure  that  no  strange  star  brighter 
than  the  fifth  magnitude  could  have  escaped  his  notice. 
•This  star  was  notable  from  the  fact  that  for  the  first 
time  the  newly  invented  spectroscope  was  applied  to  the 
study  of  temporary  stars.  The  star  was  particularly 
studied  by  Sir  William  Huggins,  who  discerned  four 

195 


THE   REVELATIONS   OF   STARLIGHT 

brilliant  lines  in  the  spectrum.  The  principal  line  re- 
presented hydrogen.  It  was  thus  obvious  that  the  cause 
of  the  outburst  was  the  eruption  of  vast  masses  of 
hydrogen  gas.  The  new  star  declined  very  rapidly  in 
brilliance,  although  not  so  rapidly  as  it  increased.  Nine 
days  after  its  appearance,  it  was  invisible  to  the  unaided 
eye.  The  remarkable  thing  about  this  star  was  that  it 
was  not  actually  a  temporary  star  in  the  true  sense  of  the 
word,  as  it  had  been  observed  ten  years  earlier  as  an 
ordinary  telescopic  star,  invisible  to  the  unaided  eye. 
The  appearance  of  this  star  caused  much  interest 
among  astronomers.  The  marvellous  feature  of  the 
outburst  was  that  in  a  few  hours  the  star  increased 
its  brilliance  by  about  nine  hundred  times.  Mr.  Peck, 
Astronomer  to  the  City  of  Edinburgh,  has  the  following 
remarks  in  this  connection  :  "  What  would  likely  be  the 
result  if  a  conflagration  like  that  which  took  place  on 
this  remote  sun  were  at  any  time  to  happen  to  our  Sun  ? 
Not  only  would  all  the  various  forms  of  life  on  Earth 
be  utterly  destroyed,  but  on  all  the  members  of  our  solar 
system  there  would  be  such  a  change  effected  that  if 
any  life  existed  even  on  the  remote  Neptune  it  would  at 
once  be  completely  extinguished.  Probably  the  life  that 
existed  on  the  whole  system  of  worlds  that  circled  round 
this  distant  star  must  have  been  annihilated,  and  as  the 
heat  and  light  of  this  star  increased  so  very  suddenly, 
there  could  have  been  given  but  short  warning  to  the 
inhabitants  of  these  worlds." 

Another  new  star  made  its  appearance  ten  years  later. 
On  November  24,  1876,  Schmidt  noticed  a  strange  star 
of  the  third  magnitude  in  Cygnus.  It  was  closely  similar  to 
the  new  star  of  1866,  hydrogen  being  present  in  abundance. 
A  new  star  which  appeared  in  Andromeda,  in  1885,  is 

196 


THE   REVELATIONS   OF   STARLIGHT 

interesting  from  the  fact  that  an  attempt  was  made  to 
measure  its  distance  from  the  solar  system.  So  vast,  how- 
ever, was  this  distance,  that  the  attempt  was  a  failure. 

The  next  temporary  star  was  detected  in  January  1 892, 
in  the  constellation  Auriga,  by  Dr.  Anderson,  of  Edin- 
burgh, a  famous  observer  of  variable  stars.  At  the  time 
of  discovery  it  was  of  the  fifth  magnitude.  Remarkably 
enough,  this  new  star  had  been  visible  to  the  unaided  eye 
for  some  time  before  Dr.  Anderson's  discovery,  but  had 
never  been  noticed.  It  had  imprinted  its  image  on 
photographs  taken  in  America  by  Professor  Pickering. 
These  photographs  showed  that  on  November  20  it  was  a 
little  over  the  fourth  magnitude.  It  then  began  to  de- 
cline, and  when  discovered  visually  it  was  of  the  fifth 
magnitude.  Then,  after  its  discovery  it  brightened  up 
again,  and  on  February  14  was  between  the  fourth  and 
fifth  magnitudes.  After  this  it  steadily  declined  until 
April,  when  it  was  of  the  fifteenth  magnitude,  but  in 
August  astronomers  were  astounded  to  find  that  it  had 
again  increased,  this  time  to  the  ninth.  Since  then  it 
has  steadily  diminished. 

A  number  of  insignificant  temporary  stars  made  their 
appearance  between  1892  and  1901,  being  mostly  detected 
by  photography  ;  these  are  of  little  interest  except  to 
the  professional  astronomer,  and  may  be  passed  over  here. 
But  on  February  21,  1901,  a  magnificent  temporary  star 
— the  most  brilliant  since  Kepler's  in  1604 — shone  out 
in  the  constellation  Perseus.  It  was  so  brilliant  as  to  be 
detected  by  a  number  of  independent  observers,  including 
Dr.  Anderson,  the  discoverer  of  the  previous  new  star, 
and  Mr.  J.  E.  Gore.  When  first  seen  by  Dr.  Anderson  it 
was  of  the  second  magnitude,  and  a  photograph  taken 
on  the  previous  evening  showed  that  it  must  have  been 

197 


THE   REVELATIONS   OF   STARLIGHT 

then  below  the  twelfth  magnitude,  as  it  was  invisible  on 
the  photograph.  On  the  evening  of  February  23  the 
star  was  equal  to  Capella,  and  of  the  first  magnitude. 
But  it  did  not  long  retain  its  pre-eminence.  By  March  1 
it  was  of  the  second  magnitude,  and  by  March  6  of  the 
third.  In  September  it  faded  to  the  sixth  magnitude, 
while  in  March  1902  it  was  of  the  eighth  magnitude, 
and  in  July  of  the  twelfth. 

Since  that  date  two  other  new  stars  have  been  dis- 
covered, both  faint,  in  1903  and  1905  respectively. 
Many  theories  have  been  advanced  to  account  for  tem- 
porary stars.  The  most  probable  of  these  various  theories 
is  that  put  forward  by  Professor  Seeliger,  who  regards 
these  outbursts  as  due  to  the  passage  of  dark  extinct 
stars  through  masses  of  nebulous  matter.  The  dark  stars 
are  raised  to  incandescence  through  friction,  just  as  the 
meteors  are  ignited  by  passing  through  the  Earth's 
atmosphere.  Temporary  stars  differ  in  many  respects 
from  variable  stars.  But  one  body  in  the  heavens,  which 
seems  to  belong  partly  to  both  classes,  deserves  mention. 
This  star  is  known  as  Eta  Argus,  and  is  invisible  in 
Europe.  At  present  it  is  of  the  seventh  magnitude,  and 
cannot  be  seen  without  the  aid  of  a  telescope.  In  the 
seventeenth  century  it  was  of  the  fourth  magnitude,  and 
a  hundred  years  later  of  the  second,  while  in  1837  it 
was  equal  to  the  first  magnitude  star  Alpha  Centauri. 
Then  it  began  to  decrease.  In  1843,  however,  it  again 
blazed  up,  and  became  the  second  star  in  the  heavens, 
surpassed  only  by  Sirius.  Since  then  it  has  steadily 
declined,  and  is  still  inconspicuous. 

There  are  many  known  variable  stars  in  the  heavens, 
the  catalogues  containing  thousands  of  them.  The  first 
variable  was  first  seen  in  1596  by  Fabricius,  a  Dutch 

198 


THE   REVELATIONS   OF   STARLIGHT 

observer.  It  is  known  as  Mira  Ceti  or  the  Wonderful  Star 
of  Cetus.  It  has  been  thus  under  observation  for  over 
three  centuries.  Its  period  is  about  331  days,  but  it 
is  not  very  regular,  and  sometimes  at  its  maximum  it  is 
much  more  brilliant  than  at  other  times.  For  instance, 
in  1906  it  was  brighter  than  the  second  magnitude.  Its 
variations  appear  to  result  from  great  internal  disturbances. 
There  are  many  stars  which  appear  to  vary  in  much  the 
same  manner  designated  as  variable  stars  of  long  periods. 

Other  two  classes  of  variables  are  known  as  "Algol 
stars,"  and  short-period  variables.  The  Algol  variables 
are  so  called  from  the  brightest  star  of  their  type,  Algol, 
or  Beta  Persei.  The  fluctuations  in  the  light  of  Algol, 
which  occupy  2  days  20  hours  48  minutes  51  seconds, 
are  believed  to  have  been  discovered  by  the  ancient 
Arabian  astronomers,  and  were  re-discovered  by  Goodricke, 
an  English  astronomer  in  1782.  Goodricke  suggested 
that  the  variations  in  the  light  of  Algol  were  caused  by  the 
partial  eclipse  of  the  star's  light  by  the  interposition  of  a 
dark  satellite  star  just  as  the  Sun's  light  is  cut  off  by  the 
Moon.  In  modern  times  the  late  Professor  Vogel  of  Pots- 
dam confirmed  this  theory  in  a  remarkable — indeed  marvel- 
lous— way  by  means  of  the  spectroscope.  The  explanation 
of  this  method  is  rather  abstruse,  and  it  is  somewhat 
difficult  to  comprehend  without  a  knowledge  of  physics. 

One  of  the  most  remarkable  uses  of  the  spectroscope  is 
due  to  the  fact  that  by  its  means  motions  may  be  measured. 
In  1842  Doppler,  a  German  physicist,  expressed  the  view 
that  the  colour  of  a  luminous  body  would  be  changed  by 
its  motion  of  approach  or  recession,  and  that  a  larger 
number  of  light  waves  would  be  entering  the  eye  of  the 
observer  if  the  body  were  approaching  than  if  it  were 
retreating.  The  late  Miss  Clerke  thus  illustrates  Doppler's 

199 


THE   REVELATIONS    OF   STARLIGHT 

principle  :  "  Suppose  shots  to  be  fired  at  a  target  at  fixed 
intervals  of  time.  If  the  marksman  advances  say  twenty 
paces  between  each  discharge  of  his  rifle,  it  is  evident  that 
the  shots  will  fall  faster  on  the  target  than  if  he  stood 
still ;  if,  on  the  contrary,  he  retires  by  the  same  amount, 
they  will  strike  at  correspondingly  longer  intervals.""  In 
an  approaching  body  the  lines  in  the  spectrum  will  be 
displaced  towards  one  end  of  it ;  on  a  receding  body 
towards  the  other.  By  this  method  several  astronomers 
succeeded  in  measuring  the  motions  of  the  stars,  and 
it  was  obvious  to  Vogel  that,  as  Algol  and  its  satellite  are 
revolving  round  a  common  centre  of  gravity,  Algol  would 
before  each  eclipse  be  retreating  from  our  system,  and 
after  each  eclipse  approaching.  Vogel  found  that  such 
was  the  case,  thus  proving  the  theory  conclusively. 

Not  only  did  he  confirm  the  theory,  but  he  has  arrived 
at  the  conclusion  that  Algol  is  a  star  1,000,000  miles  in 
diameter,  the  dark  companion  being  800,000  miles — about 
the  size  of  the  Sun.  The  distance  between  the  two  is  about 
3,000,000  miles.  From  irregularities  in  the  movements  of 
Algol,  an  American  astronomer  is  of  opinion  that  Algol 
and  its  dark  companion  revolve  round  another  dark  globe 
in  180  years,  at  a  distance  of  about  1,800,000,000  miles. 
Thus,  though  we  have  never  seen  the  satellite  of  Algol,  we 
know  that  it  exists  ;  and  though  we  cannot  tell  its  distance 
from  us,  we  can  tell  its  probable  size.  The  variable  stars  of 
short  periods,  such  as  the  famous  Beta  Lyrae,  are  also  ex- 
plained by  the  mutual  revolution  of  one  or  more  bodies,  and 
many  a  thorny  question  concerning  variable  stars  has  been 
solved  by  this  method.  Thus,  the  study  of  variable  stars 
indicates  the  existence  of  systems  of  stars — stars  in  revolu- 
tion round  their  centre  of  gravity.  This  brings  us  to  the 
subject  of  the  next  chapter — systems  of  stars. 

200 


CHAPTER   XX 

SYSTEMS   OF   STARS 

IN  the  well-known  constellation  of  the  Plough  there  is 
a  bright  star  known  as  Mizar  or  Zeta  Ursse  Majoris. 
Close  by  is  an  orb  much  fainter,  which  is  only  seen  to 
advantage  in  a  binocular  or  small  telescope.  These  two  stars, 
Mizar  and  Alcor,  form  the  finest  examples  in  the  heavens 
to  the  unaided  eye  of  what  is  known  as  a  double  star.  Other 
examples  are  to  be  found  in  Beta  Cygni,  a  magnificent  pair 
of  coloured  suns,  which  is  revealed  in  a  small  telescope, 
and  in  Alpha  Capricorni,  which  a  field  glass  will  show  as 
double.  A  considerable  number  of  double  stars  are  known. 
The  first  to  be  discovered  telescopically  was  found  in  1664, 
when  an  English  astronomer,  while  observing  a  comet  in 
the  constellation  Aries,  incidentally  noticed  that  the  star 
Gamma  of  that  constellation  consisted  of  two  stars  close 
together. 

For  many  years  it  was  believed  that  these  double  stars 
were  not  really  double,  and  that  their  apparent  connection 
was  merely  the  result  of  perspective.  It  was  supposed 
that  the  one  star  might  be  millions  or  billions  of  miles  in 
space  behind  the  other,  and  that  the  two  appeared  con- 
nected only  because  they  happened  to  lie  in  the  same  line 
*of  vision.  This  view  was  generally  held  until,  in  1802,  it 
was  shown  by  Sir  William  Herschel  that  many  double 
stars  were  real  stellar  systems.  In  that  year  he  announced 
that  in  the  case  of  many  of  these  doubles  the  two  stars 

201 


SYSTEMS   OF   STARS 

were  in  mutual  revolution — in  other  words,  that  the  law  of 
gravitation  extended  to  the  stars.  Thus  he  showed  that 
the  law  of  gravitation  which  Newton  found  applicable  to 
the  solar  system  was  not  merely  a  local  law,  but  existed 
throughout  the  length  and  breadth  of  the  Universe. 

To  distinguish  between  mere  "optical  doubles,"  of 
which  there  are  a  considerable  number  in  the  heavens, 
and  revolving  stars  he  gave  the  latter  the  name  of  "  binary  " 
stars,  and  this  name  is  retained  by  them  to  the  present 
day.  Many  of  the  brightest  stars  in  the  heavens  are 
binaries.  Among  them  must  be  mentioned  Alpha  Cen- 
tauri,  oui'  nearest  neighbour  in  space ;  Castor,  one  of  the 
two  well-known  "  Twins "  in  the  constellation  Gemini  ; 
Sirius,  the  brightest  star  in  the  sky,  and  Procyon,  another 
first- magnitude  orb.  The  detection  of  the  satellites  of 
these  two  stars  reminds  us  of  the  discovery  of  Neptune. 
In  1844,  Bessel,  the  great  German  astronomer,  discovered 
that  Sirius  was  being  attracted  off'  its  path  by  the  action 
of  some  unseen  body.  Orbits  were  calculated  by  astro- 
nomers, and  one  calculator  assigned  a  period  of  revolution 
of  about  fifty  years  to  the  satellite  star.  In  1861  the  star 
was  discovered  close  to  the  indicated  spot,  and  its  period 
of  revolution  turned  out  to  be  about  fifty  years.  In  the 
case  of  Procyon,  the  existence  of  a  satellite  star  was  also 
predicted  before  it  was  seen,  and  the  actual  period  of 
revolution  agrees  with  that  which  was  deduced  by  the 
calculators — a  fact  which  illustrates  the  remarkable  accu- 
racy of  astronomical  calculation. 

The  number  of  double  stars  in  the  heavens  is  to  be 
counted  by  thousands,  and  the  orbits  of  many  of  these 
have  been  calculated  successfully.  The  greatest  names  in 
this  department  of  astronomy  have  been  the  Herschels, 
father  and  son  ;  the  Struves,  father  and  son  ;  and  Professor 

202 


SYSTEMS   OF   STARS 

S.  W.  Burnham  of  Chicago,  the  greatest  living  observer 
of  double  stars,  who  has  himself  discovered  over  twelve 
hundred  of  these  objects. 

Thanks  to  the  spectroscopic  method  of  determining 
motion  in  the  line  of  vision,  mentioned  in  connection  with 
Algol,  many  double  stars  have  been  discovered,  the  com- 
ponents of  which  are  too  close  together  ever  to  be  separately 
seen.  Mizar  in  Ursa  Major,  which  with  Alcor  forms  a 
wide  double  and  a  connected  system,  was  found  by  Profes- 
sor E.  C.  Pickering,  by  means  of  the  spectroscopic  method, 
to  be  itself  double  ;  and  Spica,  the  brightest  star  of  Virgo, 
was  found  to  be  also  double.  In  the  case  of  the  last- 
named  star  the  companion  is  almost  completely  dark. 
Since  these  discoveries  were  made  in  1889  and  1890,  "  the 
astronomy  of  the  invisible,"  as  this  line  of  research  is  called, 
has  come  to  be  regarded  as  a  recognised  branch  of  astro- 
nomy, and  many  of  these  close  double  stars  are  now  known. 

Double  stars — that  is,  telescopic  doubles — often  exhibit 
great  varieties  of  colour.  Perhaps  the  most  beautiful 
example  within  the  range  of  small  telescopes  is  Beta 
Cygni.  A  view  of  this  beautiful  star  is  a  never-to-be- 
forgotten  spectacle.  The  larger  star  is  reddish  yellow, 
and  the  smaller  one  blue.  Antares,  a  fiery  red  star  in 
Scorpio,  of  the  first  magnitude,  is  attended  by  a  small 
green  companion  star,  and  there  are  many  other  instances. 
For  long  it  was  thought  that  star  colours  were  merely  the 
effect  of  contrast.  This,  however,  was  disproved  by 
the  spectroscopic  observations  of  Sir  William  Huggins. 
The  colours  of  the  stars  are  real.  A  vivid  description  of 
the  scene  observed  by  a  dweller  on  any  one  of  the  planets 
revolving  round  these  stars  is  given  by  the  late  Mr. 
Proctor  in  "  The  Expanse  of  Heaven.11  He  supposes  one 
of  the  suns  to  be  blue  and  the  other  orange,  the  planet 


SYSTEMS   OF   STARS 

being  placed  in  the  same  position  as  the  Earth  is  in  our 
system.  There  would  be  an  endless  variety  of  sights  in 
the  heavens.  The  blue  sun  and  orange  sun  might  rise 
together,  and  produce  "  double  day " ;  or  the  blue  sun 
might  rise  as  the  orange  sun  was  setting,  and  there  would 
be  no  night.  In  Proctor's  own  words  :  "  The  skies  must  be 
exceedingly  beautiful.  Our  clouds  have  their  silver  lining 
because  it  is  the  light  of  the  Sun  which  illumines  them. 
Our  summer  sky  presents  glowing  white  clouds  to  our 
view,  and  at  other  times  we  see  the  various  shades  be- 
tween whiteness  and  an  almost  black  hue.  .  .  .  But 
imagine  how  beautiful  the  scene  must  be  when  those  parts 
of  a  cloud  which  would  otherwise  appear  simply  darker 
shine  with  a  fuller  blue  light  or  with  a  fuller  orange 
light.  How  gorgeous  again  must  be  the  colouring  of  the 
clouds  which  fleck  the  sky  when  one  or  other  sun  is 
setting.  .  .  .  There  are  infinite  varieties  of  arrangement 
depending  on  the  relative  dimensions  of  the  suns  of  a 
double-star  system,  and  in  their  colours  there  are  immense 
varieties — yellow  and  purple  suns,  red  and  green  suns, 
suns  of  golden  yellow,  cream -white,  rose-colour,  and  so 
on  ;  companion  suns  of  lilac,  russet,  citron,  fawn,  buff,  and 
olive  hue  in  endless  numbers.  ...  I  conceive  that  few 
thoughts  can  be  more  striking  and  instructive  than  are 
those  suggested  by  this  infinite  wealth  of  beauty  and 
variety."  It  must  be  clearly  borne  in  mind  that  these 
systems  are  completely  different  from  ours.  In  the  solar 
system,  we  have  one  bright  star  and  a  number  of  planets 
revolving  round  it.  There  may  or  may  not  be  planets  in 
these  systems ;  but  if  such  worlds  do  exist,  they  will,  as 
Proctor  points  out,  certainly  experience  very  varied  sights 
in  their  skies.  Double  stars  of  all  classes  are  so  numerous 
in  the  heavens,  that  it  may  well  be  that  these  systems, 

204 


SYSTEMS   OF   STARS 

long  considered  an  exception,  may  be  as  prevalent  as  the 
systems  of  one  star,  and  a  number  of  secondary  worlds. 
Flammarion  in  his  "  Popular  Astronomy  "  has  the  follow- 
ing reflection  on  double  stars,  which  is  worthy  of  repro- 
duction, so  high  are  the  thoughts  which  it  suggests  to 
the  mind :  "  The  double  stars  are  so  many  stellar  dials 
suspended  in  the  heavens,  marking  without  stop,  in  their 
majestic  silence,  the  inexorable  march  of  time,  which 
glides  away  on  high  as  here,  and  showing  to  the  Earth 
from  the  depth  of  their  unfathomable  distance  the  years 
and  centuries  of  other  universes,  the  eternity  of  the 
veritable  Empyrean !  Eternal  clocks  of  space !  your 
motion  does  not  stop  ;  your  finger,  like  that  of  destiny, 
shows  to  beings  and  things  the  everlasting  wheel  which 
rises  to  the  summits  of  life  and  plunges  into  the  abysses 
of  death.  And  from  our  lower  abode  we  may  read  in 
your  perpetual  motion  the  decree  of  our  terrestrial  fate, 
which  bears  along  our  poor  history  and  sweeps  away  our 
generation  like  a  whirlwind  of  dust  lying  on  the  roads  of 
the  sky,  while  you  continue  to  revolve  in  silence  in  the 
mysterious  depths  of  Infinitude  !  " 

Double  stars  are  not  the  only  type  of  stellar  systems. 
There  are -triple,  quadruple,  and  multiple  stars.  One 
famous  system  is  Zeta  Cancri.  This  system  has  been  par- 
ticularly studied  by  Professor  Seeliger  of  Munich,  who  has 
shown  that  in  all  probability  three  bright  stars  in  this 
system  revolve  round  a  dark  body,  apparently  the  most 
massive  of  the  four.  From  multiple  stars  to  groups  and 
clusters  of  suns  is  but  a  step,  and  in  such  groups  as  the 
Hyades  and  Pleiades  we  have  the  next  step  in  the  scale  of 
stellar  systems.  The  group  of  the  Pleiades  is  the  most 
famous  star  group,  or  indeed  cluster,  in  the  heavens.  It 
has  been  known  from  the  earliest  ages,  and  is  referred  to 

205 


SYSTEMS   OF   STARS 

in  the  Book  of  Job  and  by  Greek  authors.  The  Pleiades, 
which  in  the  winter  months  is  one  of  the  most  noticeable 
objects  in  the  sky,  consists  of  six  or  seven  stars  visible  to 
the  unaided  eye.  Of  these  stars  the  largest  is  known  as 
Alcyone.  With  a  telescope  a  great  number  of  stars  are 
to  be  seen  in  the  Pleiades,  and  photography  has  disclosed 
the  fact  that  many  of  the  principal  stars  in  the  cluster  are 
enveloped  in  nebulous  matter.  The  Hyades,  surrounding 
the  bright  star  Aldebaran,  forms  a  more  scattered  group 
of  stars.  Another  interesting  group,  or  rather  cluster,  is 
"  Praesepe  "  or  "  the  Bee  Hive  "  in  the  constellation  Cancer. 

The  grandest  clusters  in  the  heavens  are  only  to  be 
seen  with  the  aid  of  telescopes.  Perhaps  the  two  finest  in 
the  whole  sky  are  those  in  Hercules  and  Centaur  us.  The 
cluster  in  Hercules  may  be  seen  with  the  aid  of  a  small 
telescope,  but  it  is  only  to  be  seen  with  advantage  when 
a  large  instrument  is  applied  to  it.  The  Scottish  astro- 
nomer, Nichol  of  Glasgow,  remarked  that  "  probably  no  one 
who  has  beheld  this  cluster  for  the  first  time  in  a  telescope 
of  great  power  can  refrain  from  a  shout  of  wonder." 

Let  us  consider  the  conditions  on  a  planet  situated  in 
the  middle  of  such  a  cluster  as  that  in  Hercules.  Such  a 
world  would  know  no  night.  Day  would  be  everlasting. 
If  such  a  world  turned  on  its  axis,  sun  after  sun,  blazing 
with  light  and  heat,  would  pass  across  its  sky  in  solemn 
procession.  Indeed  the  perpetual  state  of  affairs  on  such 
a  planet  is  equal  to  the  spectacle  which  we  on  Earth  should 
behold  if  all  the  stars  seen  on  the  darkest  and  clearest 
night  were  to  increase  in  brightness  until  even  the  faintest 
of  them  shone  with  a  sufficient  radiance  to  banish  night. 
Herschel  considered  that  this  cluster  contained  fourteen 
thousand  stars. 

Omega  Centauri,  only  to  be  seen  in  the  southern  hemi- 

206 


SYSTEMS   OF   STARS 

sphere,  is  a  closely  compressed  cluster  of  thousands 
of  stars.  It  may  be  seen  with  the  unaided  eye  as 
a  hazy  star,  but  a  good  telescope  is  required  to  show 
it  in  all  its  beauty  and  grandeur.  In  the  southern 
hemisphere  are  also  situated  two  remarkable  objects,  the 
Magellanic  Clouds,  individually  known  as  the  Nubecula 
Major  and  the  Nubecula  Minor.  Both  of  these  are 
roughly  of  a  circular  form.  Mr.  Gore  says  of  these 
two  clusters :  "  The  larger  cloud  covers  over  forty -two 
square  degrees,  and  when  examined  with  a  telescope  is 
found  to  consist  of  upward  of  600  stars  of  the  sixth  to 
the  tenth  magnitude,  with  numerous  fainter  ones,  and 
nearly  300  clusters  and  nebulae.  The  smaller  Magellanic 
Cloud,  Nubecula  Minor,  is  fainter  to  the  eye  and  not  so 
rich  in  the  telescope."  These  clusters  are  in  many  ways 
the  most  remarkable  objects  in  the  heavens — mighty 
collections  of  suns,  and  probably  worlds,  at  an  enormous 
distance  from  our  world.  Here  we  observe  what  Tennyson 
with  scientific  accuracy  describes  as 

"  Clusters  and  beds  of  worlds  and  bee-like  swarms 
Of  suns  and  starry  streams." 


207 


CHAPTER   XXI 

THE   MOTIONS   OF   THE   STARS 

THE  stars  are  generally  designated  as  "  fixed  "  stars 
to  distinguish  them  from  the  planets  or  "  wander- 
ing "  stars.  On  a  first  consideration  of  the  subject, 
the  name  "  fixed  stars  "  seems  to  describe  very  accurately 
the  chief  characteristics  of  these  groups.  While  the  planets 
move  about  through  the  Zodiacal  constellations,  the  stars 
preserve  relatively  to  one  another  the  same  positions. 
The  constellation  Orion  preserves  throughout  the  ages  its 
well-known  form.  Similarly  the  Plough  shines  down  on 
us  to-day  as  it  did  on  the  kingdom  of  Israel  and  on  the 
plains  of  Troy.  So  that  for  all  practical  purposes  we 
are  correct  in  speaking  of  the  fixed  stars.  And  yet, 
scientifically  speaking,  we  are  wrong.  The  stars  are  no 
more  fixed  than  are  the  planets.  Indeed,  many  of  the 
stars  are  moving  through  space  with  a  velocity  far  greater 
than  the  swiftest  of  the  planets.  But  so  distant  are  the 
stars,  so  deep  are  they  sunk  in  the  depths  of  space,  that 
in  the  course  of  hundreds,  even  thousands  of  years, 
the  casual  star-gazer  can  detect  no  difference  in  their 
positions. 

But  casual  star-gazing,  or  even  intelligent  observation 
of  the  stars  with  the  unaided  eye,  is  a  very  different  thing 
from  careful  and  patient  measurement.  The  ancient 
astronomers,  even  when  they  measured  carefully  the  posi- 
tions of  the  stars,  detected  no  change  in  their  positions, 

208 


THE   MOTIONS  OF  THE   STARS 

and  hence  they  believed  the  stars  to  be  literally  fixed  to 
the  inside  of  a  huge  sphere,  which  rotated  once  in  twenty- 
four  hours.  And  even  after  it  had  been  shown  that  the 
Earth  rotated  on  its  axis,  and  that  there  was  no  literal 
sphere,  the  idea  was  still  maintained  that  the  stars  were 
motionless. 

At  length  it  was  found  in  1715  that  the  star  Arcturus 
was  in  motion.  Halley  compared  its  position  as  noted 
by  his  own  observations  with  its  position  in  the  old 
catalogues,  and  he  found  that  unmistakably  the  star  had 
moved.  Here  was  an  extraordinary  discovery.  The  fixed 
stars  were  not  fixed.  Since  the  time  of  Halley  the  proper 
motions,  as  they  are  called,  of  many  other  stars  have 
been  measured  and  estimated,  until  at  the  present  moment, 
i*i  the  estimate  of  Professor  Dyson,  Astronomer  Royal 
of  Scotland,  the  proper  motions  of  ten  thousand  stars 
have  been  measured.  The  stars  whose  motions  have 
been  measured  travel  with  various  velocities.  The  swiftest 
star  of  all  is  an  eighth  magnitude  star  in  the  southern 
hemisphere.  This  little  object  is  not  designated  by  a 
name,  or  a  letter,  or  even  an  ordinary  number.  Its 
designation  is  "Gould's  Cordova  Zones,  V  Hour,  243."" 
This  is  the  swiftest  known  star  in  the  heavens,  and  an 
idea  of  its  vast  distance  may  be  obtained  from  the  state- 
ment that  the  star  would  require  two  hundred  years  to 
move  over  a  space  equal  to  the  Moon's  apparent  diameter. 
The  next  swiftest  star  is  an  insignificant  star  in  Ursa 
Major  which  is  known  as  "1830  Groombridge,"  that 
being  its  number  in  the  catalogue  of  the  astronomer 
Groombridge,  who  lived  early  in  the  last  century.  This 
sfcar  would  in  265  years  move  over  a  space  in  the  heavens 
equal  to  the  Sun's  apparent  diameter,  and  in  185,000 
years  would  complete  a  revolution  of  the  whole  sky. 

209  o 


THE   MOTIONS   OF  THE   STARS 

Next  to  "  1830  Groombridge  "  come  two  small  stars  in  the 
southern  hemisphere,  and  next,  our  nearer  neighbours  in 
space,  61  Cygni  and  Alpha  Centauri,  the  distances  of 
both  of  which  have  been  measured.  The  real  velocity  of 
Groombridge  1830  is  128  miles  a  second  ;  61  Cygni  moves 
at  the  rate  of  30  miles  per  second ;  while  the  bright  star 
Arcturus  has  been  calculated  to  have  a  velocity  of  no 
less  than  376  miles  per  second. 

The  Sun  is  a  star.  It  possesses  points  in  common  with 
many  of  the  suns  of  space,  and,  as  the  stars  are  moving, 
is  it  not  possible  that  the  Sun  is  also  moving  ?  At  first 
sight  it  looks  almost  impossible  to  determine  the  motion 
of  our  Sun,  if  it  does  move.  For  it  is  obvious  that  if 
the  Sun  is  moving  through  space,  the  Earth  and  other 
planets  will  be  carried  along  with  it,  just  as  the  Moon  is 
carried  along  with  the  Earth.  It  is  quite  plain,  there- 
fore, that  if  the  Sun  does  move,  there  will  be  a  corre- 
sponding displacement  of  the  stars,  just  as  there  is  in  our 
solar  system  a  displacement  of  the  Sun  resulting  from 
the  motion  of  the  Earth.  But  here  a  complication  enters 
into  the  problem.  If  the  stars  were  stationary,  it  would 
be  quite  an  easy  matter  to  detect  from  their  displace- 
ments the  motion  of  the  Sun  ;  but  they  are  not  stationary. 
Each  star  is  moving  through  space  in  its  own  particular 
direction,  and  with  its  own  particular  velocity.  Thus  the 
problem  becomes  almost  insuperable.  Nevertheless  it 
was  tackled  and  solved  over  a  hundred  years  ago,  and 
its  solution  is  one  of  those  brilliant  strokes  of  genius 
which  astronomy  owes  to  Herschel.  It  was  obvious  to 
Herschel  that  if  the  Sun  is  moving  in  a  certain  direction 
the  stars  in  front  will  appear  to  open  out  and  those 
behind  to  close  up.  Of  course,  as  already  mentioned,  this 
is  complicated  by  the  motions  of  the  stars  themselves. 

210 


From  a  photograph  taken  in  1906  by  Dr.  Max  U'olf,  of  Heidelberg 

THE  GREAT  NEBULA  IN  ORION 

This  nebula  is  generally  admitted  to  be  one  of  the  finest  sights  in  the  heavers. 


THE  MOTIONS  OF  THE   STARS 

Nevertheless  Herschel,  by  an  ingenious  method  of  sepa- 
rating the  real  from  the  apparent  motions  of  seven  stars, 
was  able  to  show  that  the  Sun  was  moving  towards  a 
point  in  the  constellation  Hercules  near  to  the  apparent 
position  of  the  star  Lambda  Herculis.  Herschel  believed 
the  rate  of  the  solar  motion  to  be  "  certainly  not  less 
than  the  Earth  has  in  her  annual  orbit.11  However,  the 
general  opinion  of  astronomers  is  that  the  velocity  of  the 
Sun  is  about  eleven  miles  per  second,  somewhat  less  than 
the  rate  of  our  planet's  motion  in  its  orbit.  It  has  now 
been  ascertained  that  the  point  towards  which  the  Sun 
is  moving  is  not  in  Hercules,  but  in  the  neighbouring 
constellation  Lyra,  near  to  the  star  known  as  Delta  Lyrae. 
If  we  give  this  great  discovery  a  moment's  consideration, 
we  cannot  but  be  impressed  with  it.  Not  only  does  the 
Earth  revolve  round  the  Sun,  but  it  follows  the  Sun  in 
its  endless  journey  through  space.  And  not  only  is  the 
Earth  moving  round  the  Sun  at  the  rate  of  eighteen  miles 
a  second,  but  it  is  being  carried  along  with  it  at  the  rate 
of  eleven  miles  a  second.  Yet  so  vast  is  the  space  sur- 
rounding the  solar  system,  and  so  completely  isolated  from 
the  rest  of  the  Universe,  that  although  the  Sun  has  been 
moving  at  the  rapid  rate  of  eleven  miles  per  second 
throughout  the  time  in  which  the  human  race  has  been 
in  existence,  yet  the  resulting  displacements  of  the  stars 
are  utterly  imperceptible  to  the  unaided  eye.  Sir  Robert 
Ball  explains  very  clearly  the  enormity  of  the  stellar 
distances  and  the  isolation  of  the  solar  system  in  the 
following  words :  "  The  Sun,  and  with  it  the  whole  solar 
»system,  is  bound  on  a  voyage  to  that  part  of  the  sky 
which  is  marked  by  the  star  Delta  Lyrae.  It  also  appears 
that  the  speed  with  which  the  motion  is  urged  is  such  as 
to  bring  us  every  day  about  700,000  miles  nearer  to  this 

211 


THE   MOTIONS   OF  THE   STARS 

part  of  the  sky.  As  you  look  at  Delta  Lyrae  to-night,  you 
may  reflect  that  within  the  last  twenty-four  hours  you  have 
travelled  toward  it  through  a  distance  of  nearly  three- 
quarters  of  a  million  of  miles.  So  great  are  the  stellar 
distances  that  a  period  of  not  less  than  180,000  years  would 
be  required  before  our  system,  even  moving  at  this  im- 
petuous speed,  could  traverse  a  distance  equal  to  that  by 
which  we  are  separated  from  the  nearest  of  the  stars." 

Mention  has  been  made  of  the  marvellous  method  of 
finding  by  means  of  the  spectroscope  the  motions  of  bodies 
in  the  line  of  vision.  In  this  way  the  motions  of  many 
stars  have  been  measured.  When  we  measure  the  "  proper 
motion  "  of  a  star  over  the  face  of  the  sky,  we  are  in  reality 
only  measuring  that  part  of  the  motion  which  is  across  the 
line  of  vision.  The  star  may  be  moving  towards  or  away 
from  the  Earth,  but  that  part  of  the  motion  could  never 
be  detected  by  the  purely  telescopic  method.  It  is  here 
that  Doppler\s  method  comes  in  conveniently.  The  first 
results  were  obtained  by  the  late  Sir  William  Huggins  as 
long  ago  as  1868.  Very  satisfactory  results  were  reached 
by  the  late  Dr.  Vogel,  who  applied  photography  to  this 
branch  of  research.  Vogel  found  that  ten  miles  a  second 
was  the  average  velocity  of  stars  in  the  direct  line  of  sight. 
Some  stars,  however,  proved  swifter,  and  some  slower  than 
the  average.  Thus  the  brilliant  star  Aldebaran  is  moving 
away  from  the  solar  system  at  the  rate  of  thirty  miles  a 
second. 

Perhaps  the  most  remarkable  fact  about  the  motions  of 
the  stars  is  that  some  stars  share  their  proper  motions 
with  others.  Flammarion  mentions  the  case  of  Regulus, 
the  brightest  star  in  Leo,  which  travels  at  the  same  rate 
as  a  faint  star  of  the  eighth  magnitude.  When  more  than 
two  stars  have  a  common  proper  motion,  the  phenomenon 


THE   MOTIONS   OF  THE   STARS 

is  known  as  "star  drift."  The  best  known  instance  is 
afforded  by  five  of  the  seven  stars  of  the  Plough.  Each 
of  these  stars  moves  with  the  same  velocity  in  the  same 
direction.  Not  only  do  these  stars  have  the  same  velocity 
across  the  line  of  sight ;  the  spectroscope  proves  that  they 
have  the  same  motion  in  the  line  of  vision  also,  so  that 
they  certainly  form  a  connected  system,  although  they 
are  separated  from  one  another  by  billions  of  miles. 

Does  any  law  regulate  the  motions  of  the  stars  ?  This 
problem  has  exercised  the  minds  of  astronomers  for  many 
years,  and  has  not  been  solved.  But  this  is  not  to  be 
wondered  at.  Even  after  the  motions  of  the  planets  were 
known  and  could  be  predicted,  the  law  of  the  planetary 
motions  was  unknown,  and  many  years,  indeed  centuries, 
elapsed  before  it  was  shown  that  the  planets  were  in 
revolution  around  the  Sun.  It  is  therefore  not  remark- 
able that  no  law  has  been  detected.  Several  speculations 
have  been  made  as  to  the  revolution  of  the  stars  round 
some  central  body.  A  well-known  German  astronomer, 
Argelander,  suggested  that  the  central  body  of  the  stellar 
system  was  situated  in  the  constellation  Perseus.  Madler, 
another  famous  German  astronomer,  after  an  elaborate  in- 
vestigation, believed  himself  to  have  obtained  satisfactory 
evidence  that  the  Sun  and  all  the  other  stars  were  in 
revolution  round  Alcyone,  the  chief  star  of  the  Pleiades  ; 
but  neither  of  these  theories  has  been  accepted,  and  at  the 
present  time  astronomers  do  not  believe  that  there  is  a  central 
sun,  large  and  powerful  enough  to  control  the  motions  of 
the  other  stars.  Flammarion,  in  one  of  his  picturesque 
'illustrations,  compares  our  solar  system  to  an  absolute 
monarchy  with  the  Sun  as  despot,  and  the  system  of  the  stars 
to  a  federated  republic  without  a  dominating  authority. 


CHAPTER   XXII 
THE    FIRE    MIST 

PERHAPS  the  most  remarkable  objects  in  the  heavens 
are  the  ha/y  celestial  clouds  known  as  nebulae,  or,  as 
they  have  been  picturesquely  called,  the  fire  mist. 
Even  with  the  unaided  eye,  two  of  the  most  famous  nebulae 
in  the  heavens  are  partly  visible.  On  a  clear  winter's  night, 
the  middle  star  of  the  "  sword  "  of  Orion  is  seen  to  be  some- 
what hazy,  and  even  a  small  hand  telescope  will  show  it  as 
a  cloud  on  the  dark  background  of  the  sky.  This  is  the 
famous  object  known  as  the  Great  Nebula  in  Orion,  con- 
sidered by  all  astronomers  to  be  one  of  the  finest  sights  in 
the  heavens.  Similarly  a  keen  eye  will  detect  a,  hazy  spot 
of  light  in  the  constellation  Andromeda,  which  the  smallest 
optical  power  resolves  into  a  nebula.  These  are  the  two 
most  famous  nebulae  in  the  heavens.  The  Andromeda  nebula 
is  the  more  easily  seen  without  telescopic  aid,  yet  the  other 
is  considered  by  far  the  grander  object  of  the  two.  Even 
in  a  small  telescope  the  Orion  nebula  is  certainly  the  more 
interesting  and  awe  inspiring.  It  was  first  observed  by  a 
Swiss  named  Cysat  in  1618,  and  it  is  somewhat  remarkable 
that  it  was  not  discovered  by  Galileo.  The  first  observation 
on  it  was  made  by  Huyghens,  who  described  the  Great 
Nebula  as  follows  :  "  In  the  sword  of  Orion  are  three  stars 
quite  close  together.  In  1656,  as  I  chanced  to  be  viewing 
the  middle  one  of  these  with  the  telescope,  instead  of  a 
single  star,  twelve  showed  themselves.  Three  of  these  almost 


THE  FIRE   MIST 

touched  each  other,  and  with  four  others  shone  through  a 
nebula,  so  that  the  space  around  them  seemed  far  brighter 
than  the  rest  of  the  heavens,  which  was  entirely  clear  and 
appeared  quite  black."  Increase  of  telescopic  power  has 
shown  the  Orion  nebula  to  be  more  and  more  complex,  until 
to-day  it  is  known  to  be  part  of  a  mighty  nebulous  system, 
enveloping  the  entire  constellation  of  Orion. 

Another  of  the  diffused  nebulae  not  visible  to  the  un- 
aided eye,  is  that  known  as  the  "  North  America  "  Nebula 
in  Cygnus.  This  nebula  was  discovered  by  Dr.  Wolf,  who 
was  so  impressed  by  its  resemblance  to  the  map  of  North 
America,  that  he  gave  it  the  name  which  it  has  retained 
ever  since.  The  great  nebula  in  Andromeda  is  a  much  less 
diffused  mass  than  that  in  Orion.  Its  distance  from  the 
solar  system  seems  to  be  very  great.  One  of  the  ablest  of 
modern  astronomers  has  calculated  its  possible  diameter, 
and  he  finds  it  to  be  so  great  that  light  would  require  many 
years  to  pass  from  one  side  of  the  nebula  to  the  other. 
It  has  been  calculated  that  if  on  a  map  of  this  object 
we  were  to  lay  down  a  map  of  the  entire  solar  system 
drawn  to  scale,  it  would  be  a  mere  speck  compared  to  the 
nebula. 

What  are  the  nebulae  ?  In  the  end  of  the  eighteenth 
century  the  general  idea  was  that  the  nebulae  were  all  star 
clusters  too  far  away  for  the  stars  composing  them  to  be 
visible  separately.  Herschel,  after  sharing  this  view  for  some 
time,  came  to  the  conclusion  that  the  nebulous  light  was 
"  not  of  a  starry  nature,"  but  was  composed  of  huge  masses 
of  glowing  gas.  There  was  nothing,  however,  to  prove  be- 
yond doubt  the  correctness  of  his  view,  and  even  Sir  David 
Brewster  in  1854,  in  "  More  Worlds  than  One,"  declared 
that  increase  of  telescopic  power  would  resolve  all  the  nebulae, 
which  in  his  view  were  all  star  clusters  at  enormous  distances. 
HerscheFs  son,  Sir  John  Herschel,  also  shared  this  view. 

215 


THE   FIRE   MIST 

Telescope  after  telescope  was  turned  on  the  nebulae  with  the 
hope  of  resolving  them  into  stars,  but  the  attempts  proved 
futile.  The  gigantic  reflector  erected  by  the  Earl  of  Rosse 
at  his  estate  in  Ireland  in  1 845,  was  turned  to  the  nebulae  in 
the  hope  that  at  last  they  would  be  resolved  into  stars.  Lord 
Rosse  himself  considered  that  he  had  partially  resolved  the 
Orion  nebulae,  and  that  a  little  increase  of  telescopic  power 
would  prove  beyond  all  doubt  that  it  was  a  star  cluster. 
The  refractor  of  Cambridge,  Massachusetts,  U.S.A.,  was 
said  to  have  also  accomplished  the  resolution  of  the  nebulae. 

Only  five  years  after  KirchofTs  discovery  of  the  principles 
of  spectrum  analysis,  Sir  William  Huggins,  on  August  29, 
1864,  turned  the  spectroscope  on  the  nebulae  in  Draco. 
The  spectrum  showed  that  the  nebulae  were  a  mass  of 
incandescent  gas.  In  Sir  William  Huggins1  own  words, 
"  these  nebulae  are  shown  by  the  prism  to  be  enormous 
gaseous  systems/1  He  then  observed  the  Orion  nebula, 
and  showed  it  to  be  also  gaseous.  After  all,  Herschel  had 
been  right,  and  other  astronomers  wrong.  Huggins  also 
proved  that  the  Ring  nebula  in  Lyra  and  the  "  Dumb  Bell " 
nebula  are  gaseous.  The  spectra  of  the  great  nebula  in 
Andromeda  and  the  great  spiral  nebula  are  more  compli- 
cated, and  they  are  considered  to  be  in  a  further  stage  of 
their  existence  than  the  great  nebulae  in  Orion. 

There  are  many  various  shapes  of  nebulae.  Some,  like 
the  Andromeda  nebula,  are  elliptical ;  others,  like  the 
Ring  nebula  in  Lyra,  annular ;  others  round  like  planets, 
and  known  as  "  planetary  nebula  "  ;  others  widely  diffused 
like  the  nebula  in  Orion  and  the  nebula  surrounding 
Eta  Argus ;  others  spiral,  like  the  nebula  in  Canes  Venatici, 
and  many  other  varieties.  Some  years  ago  the  late  Pro- 
fessor Keeler,  director  of  the  Lick  Observatory,  devoted 
himself  to  nebular  astronomy.  The  results  which  he  gained 
were  striking.  On  one  occasion  he  was  photographing 

216 


From  a  photograph  taken  in  IQCK)  by  Dr.  Max  IVolj 

THE  GREAT  SPIRAL  NEBULA 


THE  FIRE   MIST 

a  certain  nebula  in  the  constellation  Pegasus,  and  was 
amazed,  on  developing  the  plate,  to  find  that  not  only  that 
nebula  but  twenty  others  had  been  photographed.  In 
the  constellation  Andromeda  he  actually  found  thirty-two 
nebulas  reproduced  on  a  small  photographic  plate.  This 
shows  the  immense  number  of  nebulae.  He  considered  that 
with  the  Crossley  reflector,  the  instrument  with  which  he 
made  his  observations,  120,000  new  nebulae  would  be  visible, 
half  of  these  probably  spiral.  More  recently  Professor 
Perrine,  of  the  same  Observatory,  announces  that  probably 
300,000  nebulae  are  within  reach  of  the  same  instrument. 

The  gaseous  nebulae  in  the  heavens  are  to  be  counted  by 
thousands.  We  cannot  measure  the  distance  from  us  to 
any  of  them,  and  therefore  we  are  unable  even  to  estimate 
their  size.  Sir  Robert  Ball,  writing  on  the  great  nebula  in 
Orion,  says  :  "  As  the  eye  follows  the  ramifications  of  the 
great  nebula  ever  fading  away  in  brightness  until  it  dis- 
solves in  the  background  of  the  sky ;  as  we  look  at  the  multi- 
tudes of  stars  which  sparkle  out  from  the  depths  of  the  great 
glowing  gas  ;  as  we  ponder  on  the  marvellous  outlines  of  a 
portion  of  the  nebula,  we  are  tempted  to  ask  what  the  true 
magnitude  of  this  object  must  really  be.  ...  The  only 
means  of  learning  the  true  length  and  breadth  of  a  celestial 
object  depends  upon  our  having  first  discovered  the  dis- 
tance from  us  at  which  the  object  is  situated.  Unhappily 
we  are  entirely  ignorant  of  what  this  distance  may  be  in 
the  case  of  the  great  nebula  in  Orion.  .  .  .  We  shall,  however, 
certainly  not  err  on  the  side  of  exaggeration  if  we  assert 
that  the  great  nebula  must  be  many  millions  of  times  larger 
than  that  group  of  bodies  which  we  call  the  Solar  System." 

We  can  form  no  idea  of  the  appearance  of  the  nebulae 
at  close  quarters.  We  can  say  that  the  planets  are  globes 
like  the  Earth,  with  days,  nights,  seasons,  and  years ;  we 
can  assert  that  the  stars  are  suns,  like  our  Sun,  probably 

217 


THE  FIRE   MIST 

with  planets  revolving  round  them ;  we  can  even  form 
some  idea  of  what  the  scene  must  be  at  the  centre  of  a 
star  cluster ;  but  in  the  case  of  a  nebula  our  imagination 
fails.  Their  immense  size,  their  enormous  distance  from 
our  system,  and  the  mighty  changes  which  are  believed  to 
be  in  progress  in  their  midst,  show  us  in  a  new  light  the 
insignificance  of  the  Earth,  and  increase  our  astonish- 
ment when  we  remember  that  only  three  hundred  years 
ago  our  little  planet  was  believed  to  be  the  centre  of  the 
Universe. 

Many  telescopic  observations  have  been  made  on  nebula) 
in  the  hope  of  determining  whether,  like  the  stars,  they  have 
a  proper  motion,  but  all  these  attempts  have  been  futile. 
Professor  Keeler,  however,  was  successful  in  measuring  the 
velocities  often  nebulae  in  the  line  of  sight  by  means  of  the 
spectroscopic  method.  He  found  a  well-known  nebula  in 
Draco  to  be  moving  towards  the  solar  system  at  the  rate 
of  forty  miles  a  second,  and  the  Orion  nebula  to  be  receding 
at  the  rate  of  eleven  miles  a  second.  Thus  the  mighty 
fire  mists  are  sailing  through  space  on  an  endless  journey 
—just  as  the  stars  and  the  comets  are.  We  cannot  fully 
comprehend  the  meaning  of  our  own  thoughts  when  we 
reflect  that  an  enormous  diffused  mass  of  gas,  many  times 
larger  than  the  solar  system,  is  in  rapid  motion  through 
the  depths  of  space,  covering  forty  miles  in  one  second 
of  time.  Truly  the  Universe  is  more  wonderful  than 
we  can  comprehend. 


218 


CHAPTER   XXIII 
THE   GALAXY 

WHEN  we  tum  our  eyes  to  the  heavens  on  any 
clear  moonless  light,  we  cannot  but  be  impressed 
with  the  majestic  stream  of  milky  light  which 
spans  the  heavens  like  a  mighty  arch.  This  is  the  Milky 
Way,  or  Galaxy — the  ground  plan  of  the  stars.  The 
Galaxy  traverses  the  constellations  Scorpio,  Sagittarius, 
Aquila,  Cygnus,  Cepheus,  Cassiopeia,  Perseus,  Auriga, 
Gemini,  Canis  Major,  Monoceros,  Argo,  Crua,  Ara,  and 
Centaurus.  It  has  been  known  from  the  earliest  ages,  and 
many  speculations  as  to  its  true  nature  were  made  by  the 
ancient  Greeks.  In  the  opinion  of  Aristotle,  the  Galaxy 
was  due  to  atmospheric  vapours,  while  Anaxagoras  held 
the  absurd  opinion  that  it  was  the  shadow  of  the  Earth. 
Several  acute  thinkers  among  the  Greeks,  however,  were  of 
the  opinion  that  the  Galaxy  was  nothing  more  than  a  col- 
lection of  very  faint  stars,  too  faint  to  be  separately  seen. 
When  Galileo  turned  his  newly  invented  telescope  to  the 
heavens,  this  theory  was  at  once  found  to  be  the  true  one. 
For  centuries  the  Galaxy  has  arrested  the  attention  not 
only  of  men  of  science,  but  of  all  thoughtful  observers  of 
the  heavens,  and  it  is  referred  to  by  many  of  the  poets. 
Wordsworth  calls  it,  "  Heaven's  broad  causeway  paved 
with  stars,"  and  Milton's  beautiful  description  of  it  is  not 
only  poetical,  but  scientific  : — 

' '  A  broad  and  ample  road  whose  dust  is  gold, 
And  pavement  stars,  as  stars  to  thee  appear, 
219 


THE   GALAXY 

Seen  in  the  Galaxy,  that  Milky  Way, 
Which  nightly,  as  a  circling  zone  thou  seest, 
Powdered  with  stars." 

This  "  broad  and  ample  road  "  was  specially  studied  by 
Galileo  ;  but,  of  course,  his  telescope  was  far  too  small  to 
resolve  the  Galaxy  into  stars.  "  There  were  parts  of  the 
Galaxy,"  writes  Mr.  Peck,  "  that  Galileo's  telescope  utterly 
failed  to  penetrate,  and  there  still  remained  in  the  back- 
ground that  same  misty  light  which  had  for  so  many 
centuries  engaged  the  attention  of  astronomers.  With 
every  increase  of  telescopic  power,  more  stars  were  seen  and 
greater  depths  were  reached,  but  only  to  find,  as  Galileo 
had  found,  that  some  parts  would  require  a  more  powerful 
instrument  to  reveal  the  individual  stars  that  by  being 
crowded  so  closely  together  caused  this  cloudy  light.  And 
even  when  Sir  William  Herschel  applied  his  powerful  re- 
flectors to  this  part  of  the  heavens  and  reached  still  farther 
depths,  there  was  yet  seen  that  same  milky  light  which 
speaks  of  the  myriads  of  stars  still  to  be  revealed.  Nay, 
even  Lord  Rosse,  with  his  gigantic  telescope,  could  not 
resolve  some  of  the  luminous  patches  scattered  throughout 
the  Milky  Way." 

Since  the  time  of  Lord  Rosse,  photography  has  been 
applied  to  the  Galaxy  with  striking  success  by  three  dis- 
tinguished photographers  of  the  sky — Professor  Max  Wolf, 
Professor  Barnard,  and  the  late  Dr.  Isaac  Roberts.  These 
astronomers  have  shown  the  constitution  of  the  Milky  Way 
to  be  exceedingly  complex.  The  stars  are,  in  many  cases, 
intermixed  with  nebulous  matter.  Another  remarkable 
feature  of  the  Galaxy  is  the  presence  in  it  of  rifts  and 
chasms.  There  is,  for  instance,  a  typical  chasm  in  the 
southern  Milky  Way  known  as  the  "  Coal-sack  "  ;  and  there 
are  many  others.  Dr.  Wolfs  remarkable  series  of  photo- 

220 


It 


THE   GALAXY 

graphs,  too,  reveal  many  smaller  rifts  which  were  previously 
unknown.  Through  these  rifts  we  evidently  get  a  view 
into  the  depths  of  space  beyond  the  Galaxy,  into  the 
region  which  has  been  designated  the  "darkness  behind 
the  stars." 

Another  remarkable  feature  of  the  Galaxy  is  the  exist- 
ence of  streams  of  stars.  In  Cygnus,  close  to  the  star 
Deneb  or  Alpha  Cygni,  there  is  a  typical  instance  of  a 
star  stream,  which  may  be  observed  with  a  binocular. 
Many  others  of  these  are  to  be  seen  in  the  Galaxy — 
stars  obviously  connected,  which  may  yet  be  separated 
by  enormous  distances. 

Let  us  consider  what  streams  of  suns  are.  They  are 
aggregations  of  vast  orbs,  some  larger  and  some  smaller 
than  the  mighty  Sun  ;  each  of  them  possibly  the  centre  of 
a  system  of  planets,  abodes  probably  of  human  life.  It  is 
difficult  to  conceive  of  the  utter  insignificance  of  our  planet, 
indeed  of  our  Sun  and  solar  system,  compared  with  these 
mighty  star  streams.  Seen  from  these  orbs  the  Sun  itself, 
if  visible  at  all,  will  be  seen  as  a  faint  little  star,  and  the 
Earth  and  planets  of  course  will  be  totally  invisible.  If 
the  Sun  were  to  be  suddenly  extinguished,  the  consequences 
would  be  very  serious  so  far  as  our  world  and  the  other 
planets  were  concerned  ;  all  life  would  disappear  from  the 
surface  of  the  Earth,  which  would  move  through  space  as 
a  dead  world.  But  the  extinction  of  the  Sun,  with  the 
consequent  destruction  of  the  human  race,  would  be  ab- 
solutely unimportant,  if  not  unknown,  to  the  Universe  at 
large.  As  Sir  Robert  Ball  has  expressed  it :  "  All  the  stars 
'  of  heaven  would  continue  to  shine  as  before.  Not  a  point 
in  one  of  the  constellations  would  be  altered,  not  a  varia- 
tion in  the  brightness,  not  a  change  in  the  hue  of  any  star 
could  be  noticed.  The  thousands  of  nebulas  and  clusters 


THE   GALAXY 

would  be  absolutely  unaltered  ;  in  fact,  the  total  extinction 
of  the  Sun  would  be  hardly  remarked  in  the  newspapers 
published  in  the  Pleiades  or  in  Orion.  There  might 
possibly  be  a  little  line  somewhere  in  an  odd  corner  to  the 
effect  '  Mr.  So-and-So,  our  well-known  astronomer,  has 
noticed  that  a  tiny  star,  inconspicuous  to  the  eye,  and 
absolutely  of  no  importance  whatever,  has  now  become 
invisible.1  r 

The  Galaxy  is  no  mere  isolated  phenomenon  in  the 
heavens.  It  is  the  ground  plan  of  the  Universe.  It  was 
shown  by  Herschel,  a  hundred  years  ago,  that  there  are 
more  stars  in  the  regions  of  the  heavens  near  to  the  Milky 
Way  than  in  the  opposite  regions  ;  in  other  words  the 
stars  increase  up  to  the  Galaxy,  which  seems  to  be  a  region 
of  stellar  clustering.  It  has  been  shown  by  Professor 
Schiaparelli  and  the  late  Mr.  Proctor,  that  the  stars  visible 
to  the  unaided  eye  are  more  numerous  on  and  near  the 
Galaxy,  as  well  as  the  telescopic  stars.  What  light  does 
this  throw  on  the  great  question  of  the  construction  of 
the  Universe,  of  the  relation  of  the  entire  number  of  stars 
which  are  to  be  seen  with  the  most  powerful  telescope  to 
one  another,  and  to  the  Galaxy  itself?  The  prevailing 
idea  seems  to  be  that  the  entire  agglomeration  of  stars 
visible  to  the  most  powerful  telescopes,  known  as  the 
Stellar  Universe,  forms  a  globe  of  stars,  and  that  the 
Galaxy  forms  the  equatorial  zone  of  that  globe  ;  that  there 
is  greater  clustering — that  is  to  say,  that  the  stars  are 
closer  together — in  the  Galaxy  than  elsewhere  in  the 
Universe.  At  the  same  time  there  may  be  a  greater  ex- 
tension of  stars  in  the  line  of  our  vision  in  the  direction 
of  the  Galaxy. 

Although  the  above  seems  a  fairly  good  outline  of  the 
entire  Universe  of  Stars,  there  are  a  number  of  local  pecu- 


THE   GALAXY 

liarities  among  the  stars.  For  instance,  as  already  mentioned, 
stars  of  the  first  or  white  type  are  most  prevalent  on  or 
near  the  Galaxy.  The  investigations  of  Professor  Kapteyn, 
a  distinguished  Dutch  astronomer,  have  disclosed  the  fact 
that  the  near  vicinity  of  our  Sun  contains  almost  exclu- 
sively stars  of  the  solar  or  yellow  type,  the  same  class  as 
our  own  Sun.  Another  remarkable  fact  is,  that  the  stars 
in  the  constellation  Orion  have,  with  the  exception  of 
Betelgeux,  similar  spectra,  and  that  these  stars  are  closely 
intermixed  with  the  great  nebulae.  Professor  Kapteyn's 
studies  have  also  told  us  of  the  possible  existence  of 
two  great  streams  of  stars  moving  in  opposite  directions. 
These  facts  are  all  very  disconnected,  but  the  reason  of 
their  disconnection  is  that  astronomers  have  not  yet  learned 
enough  of  the  Stellar  Universe  and  of  its  dominant  feature, 
the  Galaxy,  to  form  a  complete  theory  of  its  constitution. 
As  Mr.  Gore  has  well  remarked,  "  The  Copernicus  of  the 
sidereal  system  has  not  yet  arrived,  and  it  may  be  many 
years  or  even  centuries  before  this  great  problem  is  satis- 
factorily solved." 

One  point  in  connection  with  the  system  of  the  stars, 
however,  is  tolerably  certain.  The  collection  of  orbs  which 
we  call  the  Universe  of  Stars  is  limited  in  extent.  Probably 
space  is  infinite,  but  the  number  of  stars  in  the  stellar  system 
is  not  infinite.  There  may  be  five  hundred  million  or  more, 
but  they  cannot  be  infinite  in  number.  There  is  a  well- 
known  law  of  optics  which  shows  that  if  the  stars  were 
infinite  in  number  the  whole  sky  would  shine  with  the 
brightness  of  the  Sun  as  a  result  of  the  blazing  of  an 
'infinite  number  of  suns,  extending  to  an  infinite  distance. 
In  some  parts  of  the  heavens,  too,  the  limits  of  the 
Universe  seem  to  have  been  reached.  For  instance,  at  a 
part  of  the  sky  diametrically  opposite  to  the  Milky  Way, 


THE  GALAXY 

Sir  William  Herschel  with  his  mighty  telescope  saw  a 
certain  number  of  stars.  An  Italian  observer,  Professor 
Celoria,  using  quite  a  small  instrument,  saw  exactly  the 
same  number  of  stars.  This  showed  that  HerschePs  tele- 
scope was  unable  to  show  any  more  stars  in  that  direction 
than  the  little  instrument  of  Celoria,  because  the  stars  in 
that  part  of  the  Universe  have  a  definite  limit.  At  the 
same  time  its  diameter  is  almost  unthinkable,  even  on 
the  most  moderate  estimate.  The  Universe  extends  un- 
doubtedly to  an  enormous  distance — a  distance  which  we 
can  only  estimate  and  which  we  are  unable  to  conceive. 
Yet  it  is  limited  in  extent. 

But  what,  after  all,  is  the  Stellar  Universe  ?  It  is  not 
the  Universe.  It  is  merely  one  of  a  number  of  similar 
systems  scattered  throughout  space.  We  have  never  seen 
such  systems.  Nor  can  we  expect  to  see  them.  When 
astronomers  are  still  unable  completely  to  pierce  through 
our  own  stellar  systems,  it  would  be  futile  to  expect  to 
catch  a  glimpse  of  another  system.  Reasoning,  how- 
ever, from  first  principles,  astronomers  are  on  the  whole 
inclined  to  believe  in  the  existence  of  other  systems, 
external  universes.  Mr.  Gore  has  made  a  calculation  of 
the  possible  distance  of  one  of  these  external  universes. 
Assuming  that  the  distance  of  the  nearest  of  these  systems 
is  proportionate  to  that  separating  our  system  from  Alpha 
Centauri,  he  reaches  the  astounding  conclusion  that  the 
distance  of  the  nearest  of  these  external  universes  is  no 
less  than  520,149,600,000,000,000,000  miles.  This  is, 
of  course,  pure  speculation.  The  external  universe,  if  it 
exists,  as  it  probably  does,  may  be  at  a  greater  distance, 
but  it  is  most  unlikely  to  be  any  nearer.  Our  minds  are 
overwhelmed  with  the  thoughts  suggested  by  this  calcu- 
lation. We  cannot  fully  comprehend  the  extent  of  the 


THE  GALAXY 

system  of  the  stars ;    still  less  can  we  conceive   of  an 
external  system. 

Mr.  Gore,  overwhelmed  with  the  marvels  disclosed  in 
this  calculation,  with  the  revelation  of  Infinity  which 
astronomy  gives  to  us,  closes  his  investigations  with  the 
following  beautiful  thought :  "  The  numbers  of  stars 
and  systems  really  existing,  but  invisible  to  us,  may  be 
practically  infinite.  Could  we  speed  our  flight  through 
space  on  angel  wings  beyond  the  confines  of  our  limited 
universe  to  a  distance  so  great  that  the  interval  which 
separates  us  from  the  remotest  fixed  star  might  be  con- 
sidered as  merely  a  step  on  our  celestial  journey,  what 
further  creations  might  not  then  be  revealed  to  our 
wondering  vision  ?  Systems  of  a  higher  order  might  then 
be  unfolded  to  our  view,  compared  with  which  the  whole 
of  our  visible  heavens  might  appear  like  a  grain  of  sand 
on  the  ocean  shore — systems  perhaps  stretching  to  Infinity 
before  us  and  reaching  at  last  the  glorious  '  mansions  '  .of 
the  Almighty,  the  Throne  of  the  Eternal.11 


CHAPTER   XXIV 
THE   ORIGIN   OF  THE   UNIVERSE 

ONE  of  the  most  fascinating  branches  of  astronomy 
is  that  in  which  astronomers  have  attempted  to 
discover  the  method  of  the  evolution  and  develop- 
ment of  the  Universe.  Most  of  us  believe  that,  "  In  the 
beginning  God  created  the  heavens  and  the  earth,"  and 
that  "  the  earth  was  without  form  and  void.'1  Both  of 
these  sublime  truths  are  taught  by  science  as  well  as  by 
theology.  Science  cannot  go  beyond  that ;  it  can  only 
with  all  reverence  indicate  the  method  by  which  the 
Creator  has  brought  into  existence  this  stupendous 
Universe. 

The  general  opinion  of  astronomers  is  that  the  method 
of  creation  is  disclosed  to  us  in  the  remarkable  law  of 
evolution ;  indeed,  the  law  of  evolution  as  developed  in 
the  Nebular  theory,  may  now  be  regarded  as  an  established 
scientific  truth.  The  first  hint  of  the  Nebular  theory— 
the  development  of  the  solar  system  from  masses  of 
nebulous  matter — was  given  by  the  Scottish  astronomer, 
James  Ferguson.  It  was  in  a  private  letter  that  Ferguson 
first  put  forward  his  views  of  the  Nebular  theory,  an 
effort  to  explain  the  method  of  the  Creation  as  described 
in  Genesis.  He  was  followed  by  the  German  philosopher 
Kant,  who,  in  1754,  propounded  his  views  on  the  develop- 
ment of  the  planetary  system  from  a  chaotic  nebula  or 
mass  of  incandescent  gas.  The  complete  Nebular  theory 

226 


OF  / 

THE   ORIGIN   OF   THE   UNIVERSE 

was,  however,  put  forward  independently  about  a  hundred 
years  ago  by  Herschel  and  the  French  astronomer  Laplace. 
These  two  astronomers  reached  the  Nebular  theory  by 
different  methods — Laplace  by  mathematical  reasoning, 
and  Herschel  by  direct  observation  of  the  heavens  with 
his  great  telescope. 

Laplace  noticed  that  in  the  solar  system  the  planets  all 
revolved  round  the  Sun  in  the  same  direction,  from  west 
to  east,  and  that  each  of  the  satellites  known  to  him  revolved 
round  the  planets  in  the  same  direction.  There  was  no 
obvious  reason  why  the  planets  should  revolve  in  this 
direction  more  than  in  any  other.  Another  fact  noted  by 
Laplace  was  that  all  the  planets  revolved  round  the  Sun 
and  the  satellites  round  their  primaries  in  almost  the 
same  plane  or  level  as  the  Earth  moved  round  the  Sun. 
There  was  no  obvious  reason  why  the  planets  should  all 
move  in  this  plane,  yet,  as  a  well-known  astronomer  has 
remarked,  "  there  are  a  million  chances  to  one  in  favour  of 
the  supposition  that  the  disposition  of  the  movements  of 
the  planets  has  not  been  the  result  of  chance.11  Laplace 
accordingly  put  forward  his  explanation.  This  was  that 
the  solar  system  had  originally  existed  in  the  form  of  a 
mass  of  incandescent  gas,  or  nebula.  In  contracting,  he 
pointed  out,  this  nebula  had  shed  rings  which  condensed 
to  form  the  planets,  and,  having  condensed  almost  to  its 
utmost,  now  forms  the  Sun,  the  central  body  of  the  solar 
system,  which  is  still  contracting.  Laplace  had  never  seen 
a  nebula,  for  the  simple  reason  that  he  did  not  possess  a 
telescope  ;  such  an  object  probably  existed  in  his  imagina- 
tion only.  His  great  contemporary  Herschel  had  seen 
I  hundreds  of  nebulae,  had  classified  them,  studied  them, 
i  theorised  concerning  them.  Quite  independently  of  Lap- 
!  lace,  Herschel  was  led  to  the  view  that  these  nebulae  he  was 


THE  ORIGIN  OF  THE  UNIVERSE 

observing  would  in  course  of  time  develop  into  systems 
of  suns  and  planets,  and  that  conversely  the  solar  system 
must  have  once  existed  in  the  form  of  a  great  diffused  nebula. 

Since  the  days  of  these  astronomers,  a  further  addition 
to  our  knowledge  has  been  made  by  Professor  Darwin,  of 
Cambridge.  According  to  his  researches,  millions  of  years 
ago  the  Earth  and  Moon  were  not  separate  bodies.  At 
that  time  our  planet  was  a  gaseous  mass,  spinning  on  its 
axis  in  a  very  short  period,  between  three  and  five  hours. 
In  consequence  of  this  rapid  rotation,  and  in  consequence 
of  the  tide  raised  by  the  Sun,  the  Earth  split  in  two,  and 
the  smaller  of  these  two  parts  now  forms  the  Moon.  This 
hypothesis,  rigorously  developed  by  mathematics,  is  dis- 
tinctly supplementary  to  the  Nebular  theory,  and  explains 
in  greater  detail  the  particular  development  of  that  part 
of  the  solar  domain  known  as  the  Earth-Moon  system.1 

Since  the  days  of  Herschel  and  Laplace,  astronomical 
science  has  progressed  remarkably.  The  Nebular  theory 
has  been  modified  with  the  advance  of  knowledge ;  but 
the  central  idea,  the  development  of  the  Universe,  as  we 
know  it,  from  masses  of  incandescent  gas,  is  thoroughly 
established.  Thanks  to  the  spectroscope,  that  marvellous 
instrument  by  which  we  are  enabled  to  ascertain  the  ele- 
ments of  which  Sun,  stars,  and  nebulae  are  composed,  we 
now  know  that  the  nebulae  are  really  gaseous,  a  point  on 
which  Herschel  could  merely  theorise ;  and,  what  is  even 
more  important,  we  are  enabled  to  trace  the  order  of  de- 
velopment. We  see  nebulae  and  stars  in  all  the  stages 
through  which  our  solar  system  has  passed  and  will  pass ; 
and  in  the  other  planets  of  the  solar  system  we  behold  the 
stages  through  which  our  Earth  has  passed  and  will  pass. 
By  a  careful  study  of  the  heavens  as  they  are  to-day,  we 
1  See  Chapter  XXV. 


THE   ORIGIN   OF  THE   UNIVERSE 

are  enabled  to  read  the  past  of  our  world  and  approxi- 
mately to  trace  its  future. 

In  the  heavens  we  behold  stars  and  nebulae  in  every 
stage  of  evolution.  First  of  all  we  have  the  widely  dif- 
fused nebulae  of  which  the  Orion  nebula  is  a  type.  Next 
we  have  a  more  condensed  nebula,  such  as  that  in  Andro- 
meda, and  then  the  stage  of  the  spiral  nebula.  These 
spiral  nebulae,  of  which  there  are  many  known  in  the 
heavens,  are  not  gaseous  ;  they  are  partially  solidified  and 
are  already  breaking  up  into  subordinate  centres  of  con- 
densation, which  will  in  course  of  time  become  planets  or 
small  suns.  These  larger  nebulae,  like  the  Orion  nebula 
and  the  great  spiral,  will  in  all  probability  develop  into 
clusters  of  stars.  The  smaller  nebulae  develop  into  stars 
similar  to  our  own  sun  attended  by  systems  of  planets. 
By  means  of  the  spectroscope  we  are  enabled  to  trace  the 
development  of  these  stars  after  they  pass  out  of  the 
nebulous  stage.  We  have  first  the  helium  stars  of  a 
bluish-white  tint,  in  which  the  element  helium  is  predo- 
minant, which  are  largely  gaseous  in  their  constitution ; 
next  we  have  the  white  stars  proper,  in  which  the  gases  are 
not  so  widely  diffused.  Next  we  have  the  yellow  stars, 
similar  to  our  own  sun,  orbs  in  their  prime,  slowly  but 
surely  condensing.  The  next  stage  is  that  of  the  red 
stars,  past  the  zenith  of  their  careers,  and  slowly  dying 
out.  In  this  class  are  included  many  of  the  interesting 
objects  known  as  variable  stars,  which  are  already  becom- 
ing unstable  in  their  light,  just  as  a  lamp  flickers  when  it 
is  going  out.  Lastly,  we  have  the  dark  stars  which  are 
only  known  to  exist  by  their  influences  on  the  bright  ones. 
These  orbs  are  extinct  and  dead  suns,  and  they  roll  through 
space  a  solemn  example  of  the  goal  to  which  our  Sun 
among  others  is  steadily  moving. 

229 


THE   ORIGIN   OF  THE   UNIVERSE 

The  Earth,  our  own  world,  as  we  have  seen,  has  de- 
veloped from  the  condition  of  a  little  local  condensation  in 
the  primitive  nebula.  From  the  same  condensation  has 
developed  our  satellite  the  Moon.  It  may  be  interesting 
to  trace  the  various  stages  through  which  our  Earth  has 
passed  as  exemplified  in  the  objects  in  the  heavens  around 
us.  In  the  early  stages  of  its  history,  "  the  Earth  was 
without  form,  and  void,"  as  the  Book  of  Genesis  so  simply 
and  graphically  tells  us.  In  scientific  language  the  Earth 
existed  in  the  shape  of  an  unshapely  gaseous  condensation 
in  a  chaotic  nebula.  This  was  the  first  stage  of  the 
Earth's  existence.  In  the  first  "  day  "  of  Creation — the 
Bible  tells  us — "  God  said,  Let  there  be  light ;  and  there 
was  light."  Independently  science  tells  us  the  same.  In 
passing  we  may  note  that  we  must  not  interpret  the  word 
"  day  "  as  meaning  our  terrestrial  period  of  twenty-four 
hours.  Such  a  period  did  not  exist  when  "  the  Earth  was 
without  form,  and  void,  and  darkness  was  upon  the  face  of 
the  deep." 

In  those  early  times  the  Earth  was  self-luminous.  Light 
came  into  existence  as  the  nebulous  mass  slowly  contracted. 
This  light  was  in  existence  so  far  as  the  Earth  was  concerned 
long  before  the  light  of  the  Sun.  Next  we  have  the 
period  when  the  Earth  had  solidified  so  as  to  admit  of 
the  existence  of  dry  land,  air,  and  water.  Before  this  was 
an  intermediate  period  when  the  transformation  was  being 
effected.  Professor  Lowell,  in  his  recent  work  on  "  The 
Evolution  of  Worlds,"  traces  very  completely  the  evolu- 
tion of  the  Earth  from  the  gaseous  state  to  its  present 
condition.  Not  until  the  temperature  of  the  Earth  had 
fallen  to  a  hundred  degrees  Centigrade  in  the  outer  regions 
of  the  atmosphere  could  clouds  form,  and  not  until  the 
surface  had  reached  the  same  temperature  was  it  possible 


THE   ORIGIN   OF   THE   UNIVERSE 

for  these  clouds  to  settle  on  the  surface  as  oceans.  As 
Professor  Lowell  writes :  "  Reasoning  thus  presents  us 
with  a  picture  of  our  Earth  as  a  vast  seething  cauldron 
from  which  steam  condensing  into  cloud  was  precipitated 
upon  a  heated  layer  of  rock,  to  rise  in  clouds  of  steam 
again.  The  solid  surface  had  by  this  time  formed,  thicken- 
ing slowly  and  more  or  less  irregularly,  and  into  its  larger 
dimples  the  water  settled  as  it  grew,  deepening  them  into 
the  great  ocean  basins  of  to-day." 

Later  on  the  crust  hardened,  while  the  oceans  were 
still  boiling  seas.  These  oceans,  according  to  Lowell, 
must  have  produced  a  "  small  universe  of  cloud  "  all  over 
the  Earth's  surface.  After  this  the  Earth  began  to  sustain 
the  lower  forms  of  life.  Vegetation,  the  flora  of  paleologic 
times,  flourished,  sustained  by  the  heat  of  the  Earth  itself 
below  the  cloud-masses.  So,  again  to  quote  Professor  Lowell, 
"the  flora  of  paleologic  times,  as  we  see  both  at  their 
advent  in  the  Devonian  and  from  their  superb  develop- 
ment in  the  Carboniferous  era,  consisted  wholly  of  forms 
whose  descendants  now  seek  the  shade.  These  plants, 
grown  to  the  dimensions  of  trees,  inhabited  equally  the 
tropic,  the  temperate,  and  the  frigid  zones  as  we  know 
them  now;  They  grew  right  on,  day  in,  day  out.  The 
climate,  then,  was  as  continuous  as  it  was  widespread." 

The  reason  of  the  equality  of  climate  all  over  the  globe 
was  the  fact  that  the  light  and  the  heat  of  the  Sun  were 
shut  off  by  the  great  cloud-masses  and  the  heat  was  wholly 
supplied  by  the  Earth  itself.  This  produced  the  half  light 
which  suits  the  growth  and  the  development  of  the  tree- 
ferns.  Hence  the  luxuriant  vegetation  of  ancient  days. 

By  and  by  the  clouds  dispersed.  It  was  only  then  in 
reality  that  the  year  began,  and  that  the  seasons  made  their 
appearance.  As  the  Sun  was  invisible,  and  its  rays  played 


THE   ORIGIN   OF  THE   UNIVERSE 

little  part  in  the  climate  of  the  Earth,  the  annual  re- 
volution had  no  visible  effects.  But  with  the  clearing  of 
the  sky,  the  outer  universe  came  into  existence,  so  far  as 
the  Earth  was  concerned. 

An  interesting  point  may  be  mentioned  here,  which 
Professor  I^owell  does  not  touch  on  in  his  book,  and  which 
is  indeed  seldom  dealt  with.  It  has  been  the  fashion 
among  many  scientists  to  treat  the  record  of  the  Creation 
in  the  first  chapter  of  Genesis  either  as  a  story  or  as 
an  allegorical  history.  But  it  is  somewhat  remarkable 
how  close  is  the  correspondence  between  the  Biblical 
account  and  the  latest  scientific  theory  as  developed  by 
Professor  Lowell.  After  detailing  the  bringing  forth  of 
vegetation  consequent  on  the  appearance  of  dry  land, 
which  followed  the  division  of  "the  waters  which  were 
under  the  firmament  from  the  waters  which  were  above 
the  firmament,"  the  Biblical  record  says  :— 

"  And  God  said,  Let  there  be  lights  in  the  firmament 
of  the  heaven  to  divide  the  day  from  the  night ;  and  let 
them  be  for  signs,  and  for  seasons,  and  for  days,  and  years. 
And  let  them  be  for  lights  in  the  firmament  of  the  heaven, 
to  give  light  upon  the  earth ;  and  it  was  so." 

Professor  Lowell,  who  traces  the  Earth's  history  from  a 
purely  scientific  standpoint,  says  quite  explicitly  :  "Only 
with  the  clearing  of  the  sky  did  the  seasons  come  in, 
to  register  time  by  stamping  its  record  on  the  trees. 
Before  that,  summer  and  winter,  spring  and  autumn,  were 
unknown."  He  also  shows  that  before  the  clearing  of 
the  sky  there  was  no  climate.  The  downpours  of  rain 
from  the  "  upper  waters "  must  have  been  stupendous. 
There  was  imperfect  recognition  of  day  and  night.  Dull 
sombre  days  alternated  with  nights  black  as  pitch.  "  The 
moment  the  Sun  was  let  in,  all  this  changed,  though  not 


THE  ORIGIN   OF   THE  UNIVERSE 

in  a  twinkling.  The  change  came  on  most  gradually. 
We  can  see  in  our  mind's  eye  the  first  opening  in  the 
great  welkin  permitting  the  Earth  its  initial  peeps  of  the 
world  beyond.  Eventually  the  clouds  parted  afresh  and 
farther,  and  the  Earth  began  to  open  its  eyes  to  the 
Universe  without." 

The  correspondence  is  complete  between  the  account  of 
modern  science  and  the  account  of  the  ancient  Biblical 
writer.  So  there  need  be  no  discrepancy  between  a  belief 
in  the  evolution  of  the  Earth,  as  described  by  modem 
science,  and  a  belief  in  the  accuracy  and  trustworthiness 
of  the  Biblical  record. 

Professor  Lowell  proceeds  to  trace  the  further  develop- 
ment of  our  planet  in  what  he  calls  the  "  Sun-sustained 
stage.'1  The  temperature  of  the  oceans  fell,  and  a  totally 
different  variety  of  animals  and  plants  came  into  being. 
The  oceans  were  inhabited  by  fishes  in  the  earlier  days ; 
but  after  the  clearing  of  the  skies  the  land  became  peopled 
with  different  varieties  of  animals  and  reptiles.  Then  came 
the  development  of  vegetation,  depending  on  the  change 
of  the  seasons ;  next  followed  the  coloured  flowers.  The 
Earth  became  beautiful,  clothed  with  all  the  verdure  of 
the  flowers ;  and  this  sudden  development  of  beauty  was 
due  to  the  fact  that  the  Sun  had  become  the  dominant 
factor  in  the  Earth's  organic  life.  The  Sun,  so  far  as  the 
Earth  was  concerned,  did  not  come  into  existence  until 
after  the  original  appearance  of  life  on  the  Earth.  And 
the  celestial  bodies  in  general  were  invisible  until  the 
fourth  "  day  "  or  period  of  Creation. 

Jupiter  is  a  much  larger  planet  than  ours,  and  at  a 
much  earlier  stage  of  its  evolution.  Therefore  a  careful 
study  of  it  throws  light  on  the  history  of  the  Earth.  As 
already  mentioned,  after  the  invention  of  the  telescope  it 


THE   ORIGIN   OF  THE   UNIVERSE 

was  found  that  the  visible  surface  of  Jupiter  was  diversified 
by  numerous  markings  known  as  belts.  As  astronomical 
observation  progressed,  it  was  found  that  these  were  belts 
of  dense  clouds,  so  dense  that  it  is  impossible  to  see 
through  them  the  real  surface  of  Jupiter.  It  was  originally 
supposed  by  astronomers  that  these  clouds  were  of  the 
same  nature  as  our  terrestrial  clouds  raised  up  by  the  heat 
of  the  Sun.  But  it  has  been  conclusively  shown  that  this 
is  impossible.  The  atmosphere  of  Jupiter  is  much  more 
cloudy  than  our  own,  and  yet  the  planet  is  many  times 
farther  from  the  Sun  than  the  Earth.  The  clouds  are 
certainly  raised  by  heat,  but  not  by  Sun  heat.  They  are 
raised  by  the  intense  heat  of  the  planet  itself,  which  does 
not  permit  the  vapours  to  settle  down  as  oceans,  but  raises 
them  into  the  atmosphere,  in  which  they  float  in  the  form 
of  cloud  belts.  Here,  then,  we  have  a  world  in  a  condi- 
tion similar  to  that  of  our  Earth  before  the  accomplishment 
of  the  work  of  the  third  day  of  Creation,  and  consequently 
before  the  work  of  the  fourth  day,  when  the  Sun,  Moon, 
and  stars  appeared.  Jupiter  will  not  reach  its  "  fourth 
day "  until  the  clouds  roll  away  and  the  glories  of  the 
outer  Universe  are  visible  from  the  surface  of  the  giant 
planet.  Jupiter  is  the  best  example  of  a  planet  in  an 
earlier  state  of  development  than  our  Earth.  Other 
examples  may  be  cited  in  Saturn,  Uranus,  and  Neptune. 
Each  of  these  is  much  larger  than  the  Earth,  and  each  of 
these  appears  to  be  in  a  condition  of  great  heat  and  at 
present  quite  unfitted  to  be  the  abode  of  living  creatures. 
In  Venus  we  have  a  planet  in  the  same  stage  of  planetary 
life  as  the  Earth,  because  it  is  of  the  same  size.  In  Mars 
we  have  a  stage  further.  This  planet  is  smaller  than  the 
Earth,  and  has  consequently  run  more  swiftly  through  the 
stages  of  its  evolution.  On  Mars,  planetary  old  age  has 

234 


THE   ORIGIN   OF  THE   UNIVERSE 

set  in.  The  oceans  are  all  practically  dried  up  ;  and  their 
place  has  been  taken  by  marshy  tracts  of  vegetation  ;  and 
the  atmosphere  is  very  rare. 

In  the  Moon,  our  own  satellite,  we  have  the  final  stage 
of  planetary  life.  The  Moon  is  a  dead  world.  It  has 
practically  no  atmosphere,  and  the  oceans  which  once  must 
have  existed  on  its  surface  have  completely  disappeared. 
The  surface  of  the  Moon  is  a  succession  of  very  mountainous 
regions  succeeded  by  flat  grey  barren  plains,  which  are 
supposed,  owing  to  their  low  level,  to  represent  the  old 
ocean  beds  of  the  Moon,  which  in  earlier  days  were  filled 
with  water.  The  Moon  rolls  through  space  a  dead  world, 
an  indication  of  the  future  which  awaits  our  own  planet. 

Just  as  in  a  garden,  where  we  behold  flowers  in  different 
stages  of  development,  and  may  by  the  study  of  these 
indicate  the  life-history  of  a  given  flower,  and  read  its  past 
and  future ;  just  as  in  a  forest,  by  noticing  the  various 
objects,  from  the  tender  shoot  to  the  magnificent  full- 
grown  tree,  we  are  able  to  tell  the  past  and  future  of  any 
member  of  the  group  ;  so  in  the  heavens,  by  noting  all  the 
different  stages  of  star  and  planet  life,  from  the  diffused 
nebula  to  the  dead  world  and  the  dark  star,  we  are 
enabled,  with  remarkable  accuracy,  to  read  the  past  and 
future  of  our  own  dwelling-place,  the  Earth.  To  quote 
the  reverent  remark  of  Kepler,  we  are  permitted  to  think 
the  thoughts  of  God  after  Him ;  we  are  enabled  to  trace 
in  a  partial  manner  the  marvellously  beautiful  method  by 
which  the  Creator  has  called  into  being  this  magnificent 
» Universe  in  which  we  live  ;  and  we  realise  in  a  new  light  the 
meaning  of  these  words,  "  For  My  thoughts  are  not  your 
thoughts,  neither  are  your  ways  My  ways,  saith  the  Lord :  for 
as  the  heavens  are  higher  than  the  earth,  so  are  My  ways 
higher  than  your  way  sand  My  thoughts  than  your  thoughts."'1 


CHAPTER  XXV 
THE  ROMANCE  OF  THE  TIDES 

THE  ceaseless  ebb  and  flow  of  the  ocean  has  from  the 
earliest  ages  attracted  the  attention  of  all  thought- 
ful observers  of  Nature.  The  waters  of  the  sea  are 
never  at  rest.  No  sooner  is  the  ebb  reached  than  the  flood 
begins ;  no  sooner  is  the  flood  reached  than  slowly  but 
surely  the  waters  begin  to  ebb.  Thus  for  ages,  ever  since 
the  world  was  first  formed,  the  waves  of  the  ocean  have 
beaten  on  the  shore.  And  since  scientific  speculation  and 
research  began,  the  cause  of  the  tides  has  attracted  the 
attention  of  men  of  science. 

The  study  of  the  tides  belongs  to  the  realm  of  astronomy. 
To  many  this  statement  doubtless  comes  as  a  surprise,  yet 
it  is  strictly  true.  The  tides  are  due  to  the  gravitational 
pull  on  the  Earth  of  two  celestial  bodies,  the  Sun  and  the 
Moon ;  and  the  waters,  as  the  most  easily  pulled  portion 
of  the  Earth,  are  consequently  the  parts  which  are  most 
displaced  in  position. 

The  Moon  is  chiefly  responsible  for  the  tides,  although 
the  Sun  plays  a  smaller  part  in  the  phenomenon.  Not- 
withstanding its  vast  superiority  in  size,  the  Sun  is  so  far 
away  that  its  pull  on  the  waters  is  much  less  than  that  of 
the  insignificant  Moon.  Our  satellite  plays  the  chief  part 
in  raising  the  tides.  But  the  Sun  certainly  makes  its  in- 
fluence felt.  Every  month,  there  are  two  spring  tides  and 
two  neap  tides,  as  they  are  called.  The  word  "  spring 

236 


THE   ROMANCE   OF  THE  TIDES 

tide  "  is  somewhat  misleading,  for  a  spring  tide  has  nothing 
whatever  to  do  with  the  season  of  spring.  Spring  tides, 
the  highest  tides  of  all,  are  due  to  the  fact  that  at  the 
time  the  Moon  is  either  new  or  full.  The  Sun  and  Moon 
are  both  exerting  a  pull  in  the  same  straight  line,  and  their 
combined  force  raises  a  higher  tide  than  usual.  The  lowest 
tides,  or  neap  tides,  take  place  when  the  Moon  is  at  first 
quarter  or  last  quarter.  At  these  periods  the  Sun  and 
Moon  are  tending  to  pull  the  waters  in  different  directions, 
and  the  resulting  tide  is  lower  than  the  average. 

The  tide  which  is  raised  on  the  Earth  is  made  up  of  two 
parts — the  direct  tide,  the  tidal  wave  on  the  portion  of  the 
Earth  towards  the  body  which  raises  it,  and  the  opposite 
tide  on  the  other  side  of  our  planet.  As  the  Earth  rotates 
on  its  axis  from  west  to  east,  the  watery  bulge,  as  one 
astronomer  calls  the  heaping-up  of  the  tides,  appears  to 
travel  from  east  to  west  as  a  tidal  wave  twice  in  twenty-five 
hours,  or,  to  be  more  correct,  24  hours  48  minutes,  the  time 
required  by  the  Earth  to  make  a  complete  rotation  relative 
to  the  Moon. 

Of  course  the  waters  of  the  ocean  do  not  travel  round 
the  Earth.  Only  the  form  of  the  wave  travels  from  east 
to  west.  This  wave  originates  in  the  deep  waters  of  the 
Pacific  ocean  and  travels  westward,  its  speed  varying  with 
the  depth  of  the  ocean.  The  deeper  the  waters,  the  faster 
the  velocity  of  the  wave.  As  the  wave  is  in  motion,  it 
meets  other  waves,  so  the  resultant  wave  is  not  so  simple 
as  might  be  supposed.  In  about  twelve  hours,  however,  the 
main  wave  reaches  New  Zealand,  and  in  about  thirty  hours  it 
arrives  at  the  Cape  of  Good  Hope.  Here  it  joins  two  other 
waves,  the  tide  in  the  Atlantic  off  the  African  coast  and  a 
reversed  wave,  which  has  moved  into  the  Atlantic  from  the 
other  side  of  Cape  Horn.  The  resultant  wave  travels 

237 


THE   ROMANCE   OF  THE  TIDES 

through  the  Atlantic  with  a  velocity  of  about  seven  hundred 
miles  an  hour. 

In  the  deep  oceans  there  is  little  bodily  motion  of  the 
waters.  The  waters  merely  rise  and  fall  with  a  velocity 
varying  as  their  depth,  It  is  otherwise,  however,  near  the 
coasts.  At  the  mouths  of  great  rivers  the  waters  move 
bodily  up  the  river  beds ;  similarly  on  the  sea-shore,  as  indeed 
we  know  well  from  experience.  In  the  mouths  of  some 
rivers  the  result  of  the  rising  tide  is  very  picturesque.  In 
the  case  of  the  Seine,  the  tide  surmounts  the  current  of 
the  river  and  rolls  with  increasing  velocity  up  the  river  bed. 
This  phenomenon  is  known  as  the  bore.  At  Caudebec,  on 
the  Seine,  this  phenomenon  is  especially  noticeable.  The 
following  lengthy  notice  by  the  master-hand  of  Flammarion 
is  worthy  of  quotation,  so  well  does  it  explain  this  remark- 
able spectacle : — 

"  On  the  day  and  the  hour  indicated,  the  wharf,  shaded 
with  perennial  trees  and  splendid  walks,  is  crowded  with 
spectators.  These  are  the  inhabitants  who  are  never  tired 
of  the  grand  spectacle  of  the  river  transformed,  and  strangers 
who  come  from  far  to  enjoy  and  to  study  it.  For  a  long 
time  before  the  arrival  of  the  flood  impatient  eyes  search 
the  horizon,  and  the  less  experienced  think  every  moment 
that  they  see  it  beginning  at  the  extremity  of  the  bay  which 
forms  this  bend  of  the  Seine.  A  low  murmur  announces 
its  approach  when  it  is  still  at  a  distance  of  several  miles. 
The  vast  sheet  of  water  advances  rapidly  under  a  radiant 
sun  ;  in  the  midst  of  a  verdure  which  a  zephyr  scarcely  stirs, 
there  are  all  the  motions,  all  the  agitations,  all  the  fury, 
of  a  tempest-tossed  sea.  Very  soon  the  spectacle  changes 
to  become  grander  and  more  singular  still.  The  enormous 
wave  which  marches  at  the  head  of  the  tide  swells,  rises, 
stands  up  ;  it  bursts  of  a  sudden,  and  its  summit  falls  with 


THE   ROMANCE   OF   THE   TIDES 

a  crash  ;  an  immense  roll  is  formed  and  unfolds  itself,  some- 
times from  one  end  to  the  other ;  it  is  a  cascade  which 
moves,  which  runs  and  remounts  the  river  with  the  speed 
of  a  galloping  horse.  The  flood  runs  along  like  a  wall  of 
foam,  overthrowing  all  obstacles  and  rearing  itself  up  each 
instant  like  a  gigantic  plume,  to  fall  again  quivering  on  the 
bank,  which  it  deluges.  The  ground  sometimes  trembles 
under  the  feet  of  the  spectators,  who  see,  in  less  time 
than  it  takes  to  describe  it,  the  boiling  mass  passing  on 
and  pursuing  its  ungovernable  course." 

In  England  there  is  another  famous  tide  which  rushes 
up  the  Bristol  Channel  with  a  tremendous  force.  The 
greatest  tide  in  the  world,  however,  is  to  be  seen  at  the 
Bay  of  Fundy.  Here  the  Atlantic  passes  into  a  lengthy 
channel  with  sides  which  gradually  converge.  As  the 
water  rushes  up  this  channel  it  becomes  heaped  into  a 
great  volume,  of  which  the  height  at  the  spring  tides  is 
over  fifty  feet.  In  mid-ocean  the  rise  and  fall  of  the 
waters  is  much  less  than  round  the  coasts.  The  island  of 
St.  Helena,  for  instance,  is  washed  by  a  tide  of  which  the 
height  is  only  about  three  feet. 

Wonderful  are  the  phenomena  of  the  tides  at  the 
present  time.  Mighty  are  the  forces  possessed  by  the 
rolling  waters,  but  a  scientific  study  of  the  tides  reveals 
facts  more  remarkable  than  those  which  we  have  men- 
tioned, truths  vastly  more  astounding  which  give  us  a 
glimpse  into  the  past  of  our  world  and  enable  us  to  fore- 
cast its  future.  The  mathematical  study  of  the  tides  was 
commenced  by  Sir  Isaac  Newton,  who  confirmed  by  his 
work  the  vague  notion  of  Galileo  and  Kepler,  that  the 
tides  were  caused  by  the  Sun  and  Moon.  Laplace,  the 
famous  French  mathematician,  completed  Newton's  inves- 
tigation, and  worked  out  mathematically  the  complete 


THE   ROMANCE   OF  THE   TIDES 

theory  of  the  tides.  In  more  recent  times  the  mathe- 
matical work  of  these  investigators  has  been  supplemented 
by  that  of  Professor  Sir  George  Darwin  of  Cambridge, 
whose  researches  have  given  us  a  glimpse  into  the 
shadowy  past  and  the  mysterious  future. 

Darwin  found  in  the  course  of  his  investigations  that 
the  constant  tidal  wave,  persisting  throughout  the  ages, 
acts  on  the  Earth  as  a  brake  acts  upon  a  machine.  It 
tends  to  retard  the  Earth's  motion  of  rotation  on  its  axis. 
In  other  words,  the  tides  tend  to  increase  the  length  of 
the  day  by  slowing  down  the  rate  at  which  our  world  is 
spinning. 

It  will  be  noticed  that,  so  far  as  we  know,  this  is  the 
tendency  of  tidal  action.  In  the  history  of  mankind,  the 
day  has  not  lengthened  by  even  a  small  fraction  of  a 
second,  and  we  do  not  know  from  experience  that  this 
constant  tidal  action  is  wearing  down  our  planet's  speed. 
Nevertheless,  mathematics  have  proved  this  to  be  the 
case.  Millions  of  years  are  required  for  the  results  of 
these  forces  to  become  manifest ;  so  it  is  not  surprising 
that  the  length  of  the  day  has  not  changed  appreciably 
in  the  course  of  the  few  thousand  years  during  which  the 
human  race  has  lived  on  this  planet,  and  the  few  hundred 
years  in  which  astronomers  have  determined  the  length 
of  the  day  with  any  approach  to  accuracy. 

Not  only  is  the  day  becoming  longer ;  the  Moon's 
distance  is  becoming  greater,  and  its  period  of  revolution 
is  increasing  in  length.  At  the  present  time  our  day  is 
about  twenty-four  hours  long,  and  our  month  about 
twenty-seven  days.  Darwin's  researches  show  that  with 
the  constant  friction  of  the  tides  on  the  Earth  the  day 
will  be  lengthened  at  a  more  rapid  rate  than  the  month, 
and  in  the  distant  future  the  day  and  month  will  coincide 

240 


THE   ROMANCE   OF  THE   TIDES 

in  length,  both  lasting  for  fifty -five  of  our  present  days. 
The  Moon  will  revolve  round  the  Earth  in  exactly  the 
same  period  as  our  planet  requires  to  rotate  on  its  axis, 
so  that  the  two  bodies  will  perform  their  revolution  round 
the  Sun  as  if  united  by  a  bar,  turning  the  same  face  to 
each  other.  This  is  the  future  which  the  continuous 
action  of  the  tides  holds  in  store  for  our  planet. 

Not  only  does  a  study  of  tidal  action  give  us  a 
glimpse  into  the  future  of  the  Earth  and  the  Moon. 
It  also  enables  us  to  read  the  past,  when  the  Earth 
was  in  a  plastic  condition  and  tremendous  tides  were 
raised,  not  in  the  oceans,  but  in  the  semi -liquid  crust 
of  our  planet  in  the  early  stages  of  its  history. 
According  to  Darwin,  the  Earth  in  the  remote  past  was 
rotating  on  its  axis  in  a  very  short  period,  probably 
between  three  and  five  hours.  Reasoning  backward,  we 
see  that  the  Moon  must  have  been  much  nearer  to  the 
Earth  at  that  time  than  it  is  now,  and  was  probably 
revolving  round  its  primary  in  a  period  identical  with 
that  of  the  Earth's  rotation.  The  Earth  and  the  Moon, 
then  in  a  gaseous  or  semi-gaseous  condition,  must  have 
been  revolving  almost  in  actual  contact.  This  was  a 
state  of  affairs  which  could  not  continue.  The  condition 
of  the  Moon  resembled  that  of  an  egg  balanced  on 
its  point.  The  Moon  must  either  recede  from  the 
Earth  or  fall  back  on  its  surface ;  and  had  the  month 
been  even  one  second  shorter  than  the  day,  our  satellite 
would  have  become  united  to  the  terrestrial  globe.  Here 
interposed  the  tide  raised  by  the  Sun  in  the  plastic 
jiiaterials  of  the  two  bodies,  and  the  action  of  this  tide 
caused  the  Moon  to  recede  slowly  from  its  primary  until 
it  reached  its  present  distance  of  238,000  miles. 

Now  the  fact  that  the  Earth  and  the  Moon  were  at 
341  Q 


THE   ROMANCE   OF  THE   TIDES 

this  distant  epoch  almost  in  contact,  suggests  that  they 
were  originally  in  contact  and  formed  one  body.  The 
Moon  originally  formed  part  of  the  Earth,  which  in 
consequence  of  its  very  rapid  period  of  rotation — between 
three  and  five  hours — and  also  owing  to  the  interference 
of  the  solar  tide,  split  into  two  ;  and  of  these  portions  the 
smaller  now  forms  the  Moon.  The  matter  which  now 
forms  the  Moon  may  have  been  detached  from  our  Earth 
as  a  whole  or  in  parts ;  but  it  is  almost  certain  that  it 
was  detached  from  the  Earth  owing  to  the  rapid  rotation 
of  our  planet,  which  made  a  rupture  inevitable. 

A  suggestive  speculation,  due  to  Professor  W.  H. 
Pickering,  the  well-known  American  astronomer,  is  worth 
mentioning  here,  so  full  of  interest  is  it  to  the  Earth's 
inhabitants.  Following  up  Darwin's  work,  Professor 
Pickering  considers  that  "  it  will  be  of  interest  to  deter- 
mine if  possible  from  what  part  of  the  Earth  the  Moon 
originated.1" 

"  When,11  says  Professor  Pickering,  "  the  Earth-Moon 
planet  condensed  from  the  original  nebula,  its  denser 
materials  collected  at  the  lower  levels,  while  the  lighter 
ones  were  distributed  with  considerable  uniformity  over 
its  surface.  At  the  present  time  we  find  the  lighter 
materials  missing  from  one  hemisphere.  We  find  a  large 
mass  of  material  now  up  in  the  sky,  which,  it  is  generally 
believed  by  astronomers,  formerly  formed  part  of  the 
Earth,  and  the  density  of  this  material  we  find  to  be  not 
far  from  that  of  the  missing  continents.  From  this  we 
conclude  that  this  mass  of  material  formerly  covered  that 
part  of  the  Earth  where  the  continents  are  lacking  and 
which  is  now  occupied  by  the  Pacific  Ocean."  Professor 
Pickering  also  finds  a  connection  between  the  volcanoes  of 
the  Pacific  region  and  the  volcanoes  of  the  Moon.  This, 


THE   ROMANCE    OF  THE  TIDES 

it  is  to  be  remembered,  is  merely  a  speculation,  with,  how- 
ever, "  the  balance  of  evidence  "  on  its  side.  It  certainly 
gives  a  new  interest  to  the  study  and  contemplation  of 
the  Moon,  when  we  remember  that  the  silver  orb  which 
illuminates  our  evening  skies  is  formed  of  materials  which 
once  filled  the  bed  of  the  greatest  ocean  on  the  globe. 

Another  interesting  fact  disclosed  by  Darwin's  studies 
is  that,  just  as  the  tides  raised  by  our  satellite  tend  to 
retard  the  rotation  of  the  Earth,  so  the  tides  which  the 
Earth  raises  in  the  Moon  have  the  same  effect.  There  is, 
however,  this  important  difference.  There  is  no  water  on 
the  Moon.  The  tides  raised  by  our  planet  on  the  Moon 
did  their  work  ages  ago,  when  our  satellite  was  in  a  plastic 
or  semi-liquid  condition.  The  superiority  of  the  Earth 
over  the  Moon  in  the  matter  of  size  compelled  the  Moon 
to  rotate  on  its  axis  in  the  same  period  as  it  requires  to 
revolve  round  the  Earth. 

We  may  now  briefly  sum  up  the  conclusions  to  which 
astronomers  have  been  led.  First,  we  have  a  globe  of 
molten  matter,  now  known  as  the  Earth,  turning  on  its 
axis  in  a  very  short  period.  This  very  rapid  rotation, 
assisted  by  the  tides  raised  by  the  Sun  in  both  bodies, 
caused  the  rupture  of  the  Earth  into  two  bodies,  and  the 
smaller  now  forms  the  Earth's  satellite,  which  we  call  the 
Moon.  As  a  result  of  continual  tidal  action,  the  rotation 
of  the  Moon  was  retarded,  and  it  was  forced  farther  and 
farther  from  our  planet  until  it  reached  its  present  position. 
Slowly  but  surely  the  action  of  the  Moon  in  raising  the 
jtides  of  the  ocean  is  slowing  down  the  rotation  of  the 
Earth  on  its  axis,  and  in  the  distant  future — probably  long 
after  the  Earth  is  uninhabitable  and  dead — our  planet  will 
require  fifty-five  of  its  present  days  to  rotate  on  its  axis. 

What  of  the  time  which  has  elapsed  since  the  Moon 

243 


THE  ROMANCE   OF  THE  TIDES 

was  separated  from  the  Earth  ?  This  is  a  matter  of  some 
uncertainty,  and  Professor  Darwin's  studies  place  the  period 
of  disruption  at  about  fifty-seven  millions  of  years  ago. 
The  mind  falls  back  astounded  at  such  a  statement,  and 
we  can  only  repeat  with  deeper  reverence  the  familiar 
words  — "  A  thousand  ages  in  Thy  sight  are  but  as 
yesterday  when  it  is  past." 

When  on  a  moonlight  evening  we  stand  on  the  sea-shore 
and  behold  the  ceaseless  ebb  and  flow  of  the  ocean,  with 
the  sound  of  the  waters  breaking  on  the  rocks,  we  have 
brought  to  our  minds  overwhelming  thoughts.  There  is 
the  silver  Moon  which  is  constantly  operating  on  our 
planet,  and  which,  by  means  of  this  ceaseless  ebb  and  flow 
which  its  action  causes,  is  slowly  but  surely  lengthening 
our  day  and  slowing  down  our  world.  And  by  a  study  of 
the  tides  we  have  reached  the  remarkable  conclusion  that 
the  same  silver  Moon,  our  planet's  faithful  attendant,  has 
been  constantly  travelling  farther  and  farther  from  the 
Earth  since  that  period  when  it  separated  from  our  world  ; 
and  that  period  we  have  calculated  as  fifty-seven  millions 
of  years  ago.  Truly,  of  all  the  wonders  of  modern  astro- 
nomy, there  are  few  more  astounding  than  the  romance  of 
the  tides ! 


244 


CHAPTER   XXVI 

LIGHT   AND   ITS   MYSTERIES 

THE  foregoing  sketch  of  the  Universe,  from  the  Earth 
itself  to  the  systems  of  stars  glimmering  on  the 
brink  of  Infinity,  serves  to  show  that  astronomy  is, 
after  all,  no  dry,  uninteresting  subject,  but  truly  a  fasci- 
nating and  romantic  study.  Marvellous  facts  concerning 
the  Universe  have  been  brought  to  light.  Suns  and 
planets  have  been  weighed  and  measured,  invisible  bodies 
found  by  their  influence  on  bright  ones,  comets  traced 
on  their  journeys  away  out  into  the  outer  spaces.  In 
short,  on  all  sides,  the  astronomer  has  been  the  victor  in 
the  contest  with  the  unknown.  Although,  as  Laplace 
said  when  he  was  dying,  "what  we  know  is  but  little, 
what  we  do  not  know  is  immense,"  it  is  truly  remarkable 
how  much- knowledge  of  the  Universe  has  been  gained  by 
patient  observation  and  careful  calculation  from  obser- 
vation. 

How,  then,  are  we  enabled  to  make  observations  of  the 
celestial  bodies  ?  Our  ability  is  owing  to  the  fact  that 
we  see  them — that  the  light  rays  from  these  bodies  reach 
our  Earth  and  make  known  their  existence  to  us.  Light 
therefore  bears  to  us  the  secrets  of  space.  Mention  has 
Keen  made  incidentally  in  previous  chapters  of  many  of 
the  characteristics  of  light,  and  of  its  velocity  ;  but,  so  far, 
nothing  has  been  said  of  its  real  nature.  Light  emanates 
from  the  Sun  and  stars.  The  light  from  the  Sun  falls  on 

245 


LIGHT   AND   ITS   MYSTERIES 

our  world.  We  are  bathed  in  it,  so  to  speak.  Everything 
on  the  Earth  more  or  less  reflects  the  sunlight.  Then  it 
likewise  falls  on  the  planets,  and  like  the  Earth  they  reflect 
it  back,  and  shine  by  borrowed  sunbeams.  The  stars  all 
shine  by  their  own  inherent  light,  and  send  it  through  the 
depths  of  space  for  billions  of  miles.  Light  is  a  vibration 
sent  from  the  Sun,  stars,  and  nebulae  across  the  substance 
known  as  ether,  which  fills  all  space.  But  light  does  not 
travel  instantaneously.  It  was  discovered  in  1675  by 
Roemer,  a  Danish  astronomer,  from  observing  the  eclipses 
of  the  satellites  of  Jupiter — that  these  eclipses  are  seen 
later  when  the  Earth  is  at  a  greater  distance  from  Jupiter, 
and  earlier  when  it  is  at  a  less  distance.  He  therefore 
concluded  that  light  requires  time  to  travel.  His  brilliant 
idea  was  confirmed  by  a  succession  of  illustrious  astronomers 
throughout  the  centuries,  and  they  all  agree  that  the 
velocity  of  light  is  186,000  miles  per  second.  Light,  then, 
does  not  travel  instantaneously.  On  the  Earth,  for  all 
practical  purposes,  it  does  so.  It  reaches  us  from  the  Moon 
in  a  second  and  a  half.  From  the  Sun  it  travels  in  eight 
minutes.  When  we  witness,  say,  a  great  cataclysm  begin- 
ning on  the  Sun,  we  may  know  that  it  commenced  eight 
minutes  ago,  and  that  the  light  has  been  travelling  over 
the  ninety-three  millions  of  miles  which  separate  us  from 
the  Sun  in  the  interval. 

Light,  then,  travels  at  the  enormous  velocity  of  186,000 
miles  in  one  second  of  time.  It  crosses  the  diameter 
of  the  solar  system  in  eight  hours.  It  takes  four  years 
to  reach  us  from  the  nearest  of  the  stars.  Sirius,  the 
brightest  star  of  the  sky,  is  at  a  still  greater  distance, 
for  light  requires  eight  years  to  reach  us  from  that  orb. 
Again,  light  takes  no  less  than  200  years  to  reach  us  from 
Arcturus,  one  of  the  brightest  stars  in  the  sky.  We  can 

246 


LIGHT  AND   ITS   MYSTERIES 

see  stars  whose  light  left  their  surfaces  thousands  of  years 
ago — stars  which,  for  all  we  know  to  the  contrary,  may  be 
dead  and  extinct  to-day ;  but  their  light  has  been  travel- 
ling through  space  for  all  these  centuries.  As  an  example, 
we  may  take  the  famous  new  star  in  Perseus,  which  was 
discovered  in  1901  by  Dr.  Anderson.  The  outburst  did 
not  take  place  in  the  year  1901,  which  was  merely  the  year 
that  the  light  was  first  seen  on  the  Earth.  Astronomers 
calculated  that  the  outbreak  must  have  taken  place  about 
the  year  1603,  in  the  reign  of  King  James  VI.  of  Scotland. 
The  light  from  the  new  star  was  speeding  across  the 
depths  of  space  for  three  hundred  years  before  it  reached 
this  Earth  of  ours.  The  light  which  flashed  on  the 
Earth  from  Nova  Persei  conveyed  to  the  Earth  intelli- 
gence of  a  catastrophe  which  took  place  three  centuries 
ago. 

This,  too,  is  by  no  means  an  extreme  case.  Light  takes 
several  thousand  years  to  reach  our  Earth  from  the 
boundaries  of  the  Universe.  The  various  calculations  may 
not  be  scientifically  accurate,  but  they  give  us  an  idea  of 
the  vast  distances  of  the  fainter  star-clouds  of  the  Galaxy. 
We  do  not  see  the  stars  as  they  are ;  we  see  them  as  they 
were  in  some  cases  centuries  ago. 

Mr.  Gore,  as  mentioned  in  a  previous  chapter,  has  calcu- 
lated the  possible  distance  of  the  supposed  external  uni- 
verses. Of  course  these  external  universes  have  never  been 
seen  and  we  cannot  be  certain  of  their  existence,  but, 
reasoning  from  probability,  astronomers  have  good  grounds 
for  believing  in  their  existence.  Mr.  Gore's  calculation 
places  the  nearest  of  these  universes  at  a  distance  so  vast 
that  light  takes  ninety  millions  of  years  to  reach  us  from 
its  inconceivable  distance.  The  mind  is  overwhelmed  with 
such  an  idea.  We  cannot  comprehend  ninety  millions  of 

247 


LIGHT  AND   ITS   MYSTERIES 

years ;  and  yet  this  is  only  the  nearest  of  these  universes, 
and  if  space  is  infinite  there  must  be  more.  There  will  be 
an  infinite  number  of  such  universes  scattered  throughout 
an  infinite  Cosmos.  Truly  astronomy — at  least  modern 
astronomy — is  the  science  of  infinity  and  eternity.  What 
a  vast  difference  there  is  between  the  magnificent  sweeping 
conceptions  of  modern  astronomy  and  the  primitive  and 
crude  ideas  of  the  ancient  astronomers,  who  thought  that 
the  Earth  was  the  centre  of  the  Universe  and  that  the 
stars  were  little  lamps  suspended  above  the  clouds  to  light 
up  our  planet  on  a  dark  night ! 

A  study  of  the  motion  of  light  and  its  consequent  effect 
on  the  heavens  leads  us  to  some  interesting  conclusions. 
The  stars  are  at  different  distances,  and  consequently  light 
takes  longer  to  reach  us  from  some  than  from  others.  For 
instance,  light  travels  from  Sirius  in  eight  years  and  from 
Arcturus  in  over  two  hundred  years.  The  result  of  this 
is  that  we  never  see  the  stellar  system  as  it  is  at  present 
or  even  as  it  was  at  any  given  time.  Each  of  the  stars 
which  we  see  is  at  a  particular  distance  of  its  own.  One 
may  appear  to  us  as  it  was  twenty  years  ago,  another  as  it 
was  a  thousand  years  ago.  We  see  what  we  may  call  the 
"  ancient  light "  of  the  various  stars.  Now  let  us  suppose 
that  astronomers  were  able  to  construct  telescopes  large 
enough  not  only  to  enormously  magnify  the  stars  but  to 
show  the  planets  which  are  revolving  round  them,  and  the 
events  which  are  happening  on  the  surface  of  these  planets. 
Could  we  observe  these  planets  we  should  not  see  the  events 
which  are  happening  at  this  moment,  but  the  events  of 
years  ago,  because  light  takes  time  to  travel.  In  the  case 
of  a  planet  revolving  round  Sirius  we  should  see  not  the 
events  of  the  present  time  but  the  events  of  eight  years 
ago.  If  there  are  inhabited  planets  revolving  round  Sirius 

248 


LIGHT   AND   ITS   MYSTERIES 

then  their  light  is  combined  with  the  blaze  of  their  primary. 
Could  we  disentangle  the  rays  and  see  these  planets  and 
their  inhabitants  we  should  behold  what  was  enacted  on 
their  surface  eight  years  ago. 

We  may  now  invert  the  idea  and  apply  it  to  our  own 
Earth.  As  an  American  astronomer  has  expressed  it,  "  the 
light  from  every  human  action  performed  under  a  clear 
sky  is  still  pursuing  its  course  among  the  stars."  Suppose 
that  in  some  of  the  planets  revolving  round  the  stars  there 
exist  astronomers  who  have  built  telescopes  large  enough 
not  only  to  see  the  planets  revolving  round  the  Sun,  but 
to  see  the  Earth,  its  various  nations  and  peoples,  and 
what  is  going  on  on  its  surface.  At  the  distance  of  the 
nearest  star  our  Sun  is  reduced  to  a  star  of  the  second 
magnitude,  and  all  the  planets  are  lost  in  the  solar  glare, 
still  the  idea  is  correct.  The  astronomers  on  planets 
revolving  round  Sirius  would  see  the  Earth  as  it  was 
eight  years  ago.  Similarly  the  people  on  planets  moving 
round  the  Pole  Star  would  see  the  Earth  as  it  was  forty- 
nine  years  ago.  Likewise,  on  Arcturus  the  Earth  would 
appear  as  it  was  two  hundred  years  ago.  Supposing  that 
from  these  stars  and  planets  not  only  the  Earth  but  the 
countries  on  its  surface,  even  the  little  country  called 
Great  Britain,  could  be  seen,  the  inhabitants  of  some  of 
them  would  only  now  be  witnessing  the  Battle  of  Bannock- 
burn  ;  others  further  away  would  now  behold  the  Battle 
of  Hastings.  Still  further  away  others  would  see  our 
country  inhabited  by  wild  animals. 

What  does  all  this  teach  us  ?  It  teaches  us  that  there 
is  no  such  thing  as  the  past.  The  events  of  ancient 
history,  for  instance,  are  past  so  far  as  we  are  concerned, 
but  they  are  not  past  in  reality.  The  light  from  them 
is  still  speeding  onwards  from  them  through  space.  As 


LIGHT   AND    ITS   MYSTERIES 

Flammarion  expresses  it :  "  The  progressive  motion  of 
light  carries  with  it  through  Infinity  the  ancient  history 
of  all  the  suns  expressed  in  an  eternal  present.  Events 
vanish  from  the  place  which  brings  them  forth,  but  they 
remain  in  space." 

Of  all  the  romances  of  astronomy  this  is  the  most 
romantic.  Yet  it  is  all  strictly  true.  It  is  obvious  that 
we  are  now  treading  on  half  explored  ground,  for  we  have 
neither  the  ability  nor  the  instrumental  power  necessary 
for  us  to  realise  the  truth  of  Flammarion's  statement. 
For  instance,  we  only  measure  time  in  days  and  years  be- 
cause we  live  on  a  little  planet  revolving  round  a  star. 
Away  out  in  space  there  is  no  such  thing  as  a  period  of 
time,  because  there  is  no  method  of  measuring  time.  And 
when  we  cannot  measure  time  we  cannot  think  of  a  past ; 
everything  is  present.  The  whole  subject  is  overwhelming 
and  beyond  our  conception.  With  our  limited  under- 
standings we  cannot  grasp  it  in  its  entirety.  In  our  pre- 
sent existence  we  only  see  these  marvels  "  through  a  glass, 
darkly."  Still,  here  again,  we  find  the  oldest  of  the 
sciences  aiding  us  in  our  comprehension  of  religion,  and 
we  at  last  grasp  the  meaning  of  the  deep  saying  of  Carlyle 
that  to  God  there  is  neither  past  nor  future,  but  all  is  an 
eternal  Now. 


250 


CHAPTER   XXVII 
HOW  TO    KNOW   THE   STARS 

PERHAPS  no  one  can  really  appreciate  the  romance 
of  astronomy  without  being  familiar  with  the 
brighter  stars  and  the  principal  constellations.  As 
Mr.  E.  W.  Maunder  puts  it :  "  How  great  an  interest  is 
given  to  any  object  by  the  fact  that  we  know  its  name. 
Take  some  town  children  out  into  the  country,  and  set 
them  to  gather  wild  flowers,  how  instantly  they  ask  their 
names."  It  is  the  same  in  the  case  of  the  stars.  When 
we  look  at  the  heavens  on  a  clear  night  and  behold  appa- 
rently countless  points  of  light,  we  are  lost  and  over- 
whelmed with  the  number  of  the  stars  and  the  complexity 
of  their  distribution.  One  star  seems  much  like  another, 
and  we  look  away  from  the  sky  again  with  neither  interest 
nor  curiosity.  But  if  we  are  told  that  such  and  such  a  star 
is  Aldebaran,  and  such  and  such  is  Sirius,  our  interest  is 
aroused,  and  we  naturally  desire  to  trace  out  the  star  groups 
in  the  heavens  and  to  identify  the  stars  for  ourselves. 

"  But,"  asks  the  would-be  astronomer,  "  how  is  it  pos- 
sible for  me  to  learn  the  star  names  and  trace  the  constel- 
lations without  being  taught  ? "  Carlyle  lamented  in 
his  old  age,  "  Why  did  not  somebody  teach  me  the  con- 
stellations and  make  me  at  home  in  the  starry  heavens  ?  " 
But  in  reality  no  one  requires  to  be  taught  the  constella- 
tions. Every  one  can  best  learn  them  for  himself.  At 
the  outset,  it  is  true,  the  task  seems  impossible  of  attain- 

251 


HOW  TO   KNOW   THE   STARS 

ment,  and  some  of  the  hints  given  in  astronomical  books 
only  make  the  task  seem  more  gigantic.  When  we  are 
told  to  draw  imaginary  lines  through  such  and  such  stars 
of  the  Plough  and  these  will  lead  us  to  such  and  such 
stars  in  Leo,  and  will  form  triangles  and  quadrilaterals 
with  such  and  such  stars  in  Cepheus,  we  feel  baffled  with 
the  magnitude  of  the  task,  and  many  would-be  astronomers 
fall  back  in  despair  and  become  star-gazers  pure  and  simple. 
Now  this  geometrical  method,  as  we  might  call  it,  is  all 
very  well  after  we  have  acquired  a  knowledge  of  the  chief 
constellations  ;  it  will  then  aid  us  in  identifying  the  various 
stars  of  these  constellations.  But  it  is  open  to  very  serious 
objections  when  we  are  studying  the  heavens  for  the  first 
time.  Instead  of  this  method  there  is  another  which,  for 
want  of  a  better  term,  we  may  call  the  pictorial  method. 
The  beginner  should  first  possess  himself  of  a  revolving 
planisphere,  which  shows  the  heavens  at  the  various  seasons 
of  the  year,  and  which  is  of  a  convenient  size  to  be  taken 
out  of  doors.  He  should  then  decide  which  part  of  the 
heavens  he  wishes  to  consider,  and  having  selected,  say  the 
Southern  aspect,  he  should  adjust  the  planisphere  to  the 
day  and  hour  and  examine  it  with  the  aid  of  a  lantern. 
He  will  be  surprised  to  find  that  he  can  trace  without  dif- 
ficulty in  the  heavens  the  forms  which  he  sees  on  the  plani- 
sphere and  the  names  of  which  he  learns.  He  sees,  for 
instance,  on  the  planisphere  a  particular  group  in  the  form 
of  a  cross  high  up,  and  named  "Cygnus."  When  he  turns 
his  gaze  to  the  heavens,  there  he  can  trace  this  form  with- 
out difficulty.  Where  a  few  minutes  ago  he  could  only  see 
an  irregular  mass  of  stars,  he  now  sees  a  star  group  with  a 
distinct  form  and  its  own  individuality.  Similarly  the  ob- 
server will  pick  up  other  groups  in  the  same  manner.  No 
attempt  should  be  made  to  force  the  recollection  of  the 

252 


HOW  TO   KNOW  THE  STARS 

groups,  but  the  observer  should  return  night  after  night  to 
the  same  part  of  the  heavens.  He  will  be  surprised  to  find 
that  he  is  beginning  to  know  the  constellations  without  any 
effort ;  the  configurations  are  becoming  familiar  to  him, 
and,  after  a  few  nights1  comparison  of  the  heavens  and  the 
planisphere,  he  will  be  able  to  identify  Cygnus,  Aquila, 
&c.,  without  the  aid  of  the  planisphere.  In  this  manner 
the  observer  may  in  the  course  of  a  few  months  learn  all 
the  various  constellations.  The  names,  too,  of  the  bright- 
est stars  are  marked  in  the  planisphere,  and  he  will  thus 
unconsciously  learn  them  also.  For  instance,  he  will  see 
that  one  of  the  stars  in  Lyra  is  very  bright.  Looking  at 
the  planisphere  he  will  see  that  it  is  thereon  designated 
by  a  special  name,  "  Vega  "  ;  and  thus  a  knowledge  of  the 
brighter  stars  individually  is  easy. 

Many  are  content  with  a  knowledge  of  the  constellations 
and  bright  stars,  but  it  is  well  to  be  familiar  with  most  of 
the  stars  of  the  second  magnitude  as  well,  and  also  some 
stars  of  the  fainter  magnitudes.  For  this  purpose,  of 
course,  the  planisphere  is  of  no  use.  The  observer  should 
consult  some  star  maps  or  atlas  of  the  stars.  But  he 
should  be  particularly  careful  in  his  choice  of  star  maps. 
By  all  means  let  him  avoid  those  on  which  are  represented 
what  are -known  as  "the  constellation  figures."  In  such 
maps  we  find  the  Plough  represented  by  the  figure  of  a 
bear  dotted  with  stars,  Cygnus  by  a  star-spangled  swan, 
Orion  by  a  hunter  marked  with  stars.  The  stars  are  all 
inserted  and  named,  but  they  are  lost  and  confused  through 
the  introduction  of  the  constellation  figures.  These 
figures  are  very  interesting  to  the  antiquarian  and  to  the 
astronomer  who  studies  closely  the  beginning  of  the  science, 
*  but  they  are  utterly  out  of  place  on  such  star  maps.  They 
existed  and  exist  only  in  the  imaginations  of  men  and 

253 


HOW   TO   KNOW  THE   STARS 

have  no  counterpart  in  the  heavens.  Whatever  maps  the 
would-be  astronomer  uses,  he  should  use  maps  on  which 
only  the  actual  stars  are  marked.  Various  excellent  maps 
could  be  mentioned.  In  "  A  Handbook  and  Atlas  of  As- 
tronomy,'1 by  Mr.  William  Peck,  Astronomer  to  the  City 
of  Edinburgh,  there  is  a  good  series  of  charts  respecting 
regions  in  the  heavens  which  should  be  of  much  use  to  the 
observer.  If  the  observer,  however,  wishes  to  study  not 
regions  but  individual  constellations,  he  should  at  once 
possess  himself  of  Mr.  J.  E.  Gore's  excellent  guide  entitled 
"  Star  Groups.""  This  latter  method  of  learning  the  in- 
dividual stars  is  really  the  best.  Once  the  form  of  the 
constellation  is  mastered  with  the  aid  of  the  planisphere, 
the  observer  is  familiar  with  the  constellation's  form  and 
can  study  each  star  group  individually.  At  this  stage  of 
his  knowledge  he  will  find  Mr.  Gore's  book  of  the  utmost 
value.  The  constellations  are  represented  on  separate 
maps  and  there  are  no  constellation  figures,  nor  even  any 
degees  of  measurement.  The  stars  are  shown  in  white 
on  a  black  background,  and  with  the  aid  of  this  book  and 
a  lantern  the  observer  will  not  only  have  mastered  the 
constellations,  but  will  have  gained  sufficient  knowledge 
of  the  heavens  to  enable  him  to  begin  astronomical  obser- 
vation on  his  own  account. 

Nothing  has  been  said  here  of  the  identification  of  the 
planets,  and  nothing  need  be  said.  The  student  will 
find  no  difficulty  in  recognising  the  planets  ;  he  will  soon 
learn  to  recognise  the  dull  yellow  glare  of  Saturn,  the  soft 
golden  glow  of  Venus,  the  steady  shining  of  Jupiter,  the 
ruddy  beams  of  Mars.  He  may  even  succeed  in  catching 
a  glimpse  of  the  elusive  wanderer,  Mercury,  "  the  sparkling 
one,"  on  some  evening  or  morning  when  the  horizon  is 
clear  and  the  planet  well  placed  for  observation. 


HOW  TO   KNOW  THE   STARS 

As  mentioned  in  a  previous  chapter,  with  the  changes 
of  the  seasons  new  star  groups  appear,  old  star  groups 
disappear.  In  the  South  we  behold  the  stately  procession 
of  the  stars  nightly  across  the  skies.  Leo,  Virgo,  Gemini 
in  spring  ;  Bootes,  Scorpio,  Hercules  in  summer  ;  Cygnus, 
Aquila,  Cetus  in  autumn ;  Orion,  Taurus,  Canis  Major, 
Perseus  in  winter.  While  the  Plough  and  the  Cassiopeia, 
and  the  other  northern  stars  surrounding  the  Pole  Star 
circle  slowly  round  as  the  months  go  by.  As  the  seasons 
advance  the  reappearance  of  a  familiar  constellation  lends 
a  new  charm  and  interest  to  the  evening  walk.  As  Mr. 
Maunder  has  well  said,  the  work  of  learning  the  stars  "  has 
a  charm  of  its  own.  The  silent  watchers  from  heaven 
soon  become  each  a  familiar  friend,  and  to  any  imagina- 
tive mind  the  sense  that  he  is  treading  the  same  path  as 
that  traversed  by  the  first  students  of  Nature  will  have  a 
strange  charm."" 

Once  the  observer  has  learned  the  constellations  he  is 
able  to  commence  systematic  observation  on  his  own 
account.  Even  with  the  unaided  eye  he  may  accomplish 
work  which  will  at  least  afford  him  pleasure  if  it  does  not 
add  to  the  sum  of  knowledge.  With  a  field-glass  we  may 
make  many  interesting  observations,  while  quite  a  number 
of  celestial  spectacles  are  open  to  the  observer  possessing 
a  telescope  of  two  inches  aperture. 

In  the  following  list  an  account  is  given  of  the  chief 
objects  of  interest  in  the  chief  constellations  in  alphabeti- 
cal order — 

Andromeda. — The  most  interesting  object  in  this  constellation 
is  the  great  nebula.  It  may  be  glimpsed  with  the  un- 
aided eye,  and  is  easily  seen  with  a  field-glass.  In  a 
2-inch  telescope  it  is  a  very  fine  spectacle.  The  chief 
stars  are  Alpha,  Beta,  and  Gamma  of  the  second  magni- 
tude, and  Delta  of  the  third. 
255 


HOW  TO   KNOW   THE   STARS 

Aquarius. — One  of  the  Zodiacal  constellations  and  incon- 
spicuous. Its  chief  stars  are  Alpha  and  Beta  of  the 
third  magnitude,  Delta  and  Zeta  between  the  third  and 
fourth. 

Aqvila. — A  very  striking  group.  Well  seen  in  summer  and 
autumn.  The  chief  stars  are  Alpha  (Altair)  of  the  first 
magnitude,  and  Beta  and  Gamma  of  the  third.  The 
three  are  on  a  line.  The  star  Eta  is  a  short  period 
variable  with  a  period  of  seven  days.  It  is  easily  followed 
with  the  unaided  eye.  The  Galaxy  is  very  brilliant  in 
this  constellation. 

Aries. — A  small  compact  constellation.  The  brightest  stars 
are  Alpha  and  Beta  of  second  and  third  magnitude  respec- 
tively. Aries  is  the  first  of  the  Zodiacal  constellations. 

Auriga. — One  of  the  most  notable  of  the  constellations  and  a 
good  group  for  binocular  observation.  The  brightest  stars 
are  Alpha — the  brilliant  Capella — of  the  first  magnitude, 
and  Beta  of  the  second. 

Bootes. — A  straggling  constellation  which  Mr.  Maunder 
believes  to  resemble  the  much  more  striking  group  of 
Orion.  The  brightest  star  is  Arcturus,  or  Alpha  Bootis, 
of  the  first  magnitude.  Delta  shows  in  the  field-glass  as 
a  double  star. 

Cancer. — This  is  the  smallest  and  most  inconspicuous  of  all  the 
Zodiacal  constellations.  The  only  striking  feature  of  the 
group  is  the  cluster  known  as  Praesepe  or  the  Bee-hive. 
It  is  visible  to  the  unaided  eye  as  a  nebulous  object,  but 
the  least  optical  aid  shows  it  to  be  a  group  of  stars. 

Canes  Venatici. — This  is  a  very  small  constellation  containing 
only  one  conspicuous  star,  Alpha,  known  otherwise  as 
Cor  Caroli. 

Cams  Major. — This  group  of  stars  lies  too  low  down  to  be  seen 
to  full  advantage  in  this  country.  Nevertheless  it  is  a  very 
fine  celestial  spectacle.  Alpha,  or  Sirius,  is  the  brightest 
star  in  the  sky.  It  forms  with  Betelgeux  in  Orion  and 
Procyon  in  Canis  Minor  an  equilateral  triangle.  Al- 
though the  study  and  identification  of  the  stars  on  the 
principles  of  lines  and  triangles  is,  generally  speaking, 
to  be  avoided,  this  is  a  figure  so  regular,  so  massive,  that 
no  one  can  mistake  it,  and  it  is  useful  to  remember  the 
names  of  the  three  stars  which  form  it.  The  brilliance 
of  the  three  and  the  dearth  of  brightness  within  the  figure 
make  it  a  majestic  feature  of  the  heavens,  The  following 
256 


HOW  TO   KNOW  THE   STARS 

ancient  rhyme  quoted  by  Admiral  Smyth  should  assist 
the  beginner  Jin  remembering  these  stars — 

"  Let  Procyon  join  to  Betelgeux 
And  pass  a  line  afar 
To  reach  the  point  where  Sirius  glows. 
The  most  conspicuous  star, 
Then  will  the  eye  delighted  view 
A  figure  fine  and  vast, 
Its  span  is  equilateral, 
Triangular  its  cast." 

Cants  Minor. — A  very  limited  group.  Its  brightest  star  is 
Procyon,  of  the  first  magnitude. 

Capricornus. — This  constellation  is  a  good  field  for  the  bino- 
cular. Alpha  of  the  third  magnitude  is  a  visual  double 
star  and  is  well  seen  with  the  binocular.  It  is  not  a  true 
double  star,  as  the  two  stars  are  travelling  in  different 
directions,  and  merely  appear  to  be  connected  because 
they  happen  to  lie  in  the  same  line  of  vision. 

Cassiopeia. — No  one  can  fail  to  recognise  this  constellation, 
shaped  like  the  letter  W,  which  is  on  the  opposite  side  of 
the  Pole  Star  from  the  Plough.  It  is  a  good  binocular  field. 
The  region  round  the  star  Gamma  is  a  particularly  interest- 
ing one.  The  star  Alpha  is  slightly  variable  in  light. 

Cepheus. — A  less  conspicuous  group  than  the  former.  Viewed 
with  the  binocular,  however,  there  are  some  fine  star-fields. 
A  notable  triangle  is  formed  by  the  stars  Delta,  Zeta,  and 
Epsilon.  Of  these  Delta  is  a  variable  star  from  the  third 
to  the  fourth  magnitude,  with  a  period  of  5  days  8  hours. 
In  the  same  constellation  is  Mu  Cephei,  the  reddest  star 
visible  to  the  unaided  eye.  It  is  of  the  fourth  magnitude, 
and  was  called  by  Herschel  "the  Garnet  Star."  It  is 
a  striking  spectacle  in  the  binocular. 

Cetus. — A  long  straggling  group  somewhat  difficult  to  follow. 
Beta,  the  brightest,  is  of  the  second  magnitude.  The 
most  notable  star  in  the  constellation  is  Omicron,  known 
as  Mira,  "the  wonderful  star."  It  is  a  notable  variable 
with  a  period  of  331  days.  At  maximum  its  variation 
may  be  easily  followed  by  the  unaided  eye. 

Corona  Borealis. — There  is  not  the  slightest  difficulty  in 
identifying  this  constellation.  Its  name,  "  the  Northern 
Crown,"  suits  it  exactly,  and,  from  its  crown  shape,  is  easily 
identified.  Its  brightest  star,  Alphecca,  of  the  second 

257  R 


HOW   TO   KNOW  THE   STARS 

magnitude.     It  is  a  good  field  for  the  binocular.     In  this 
constellation  appeared  the  "blaze  star"  of  1866. 

Corvus  and  Crater. — These  are  two  small  insignificant  constel- 
lations seen  in  the  South  in  the  spring-time.  They  pre- 
sent little  of  interest  to  the  beginner. 

Cygnus. — This  is  one  of  the  finest  constellations  in  the  entire 
heavens.  The  Galaxy  is  here  particularly  rich,  and  fine 
fields  are  within  the  reach  of  the  binocular.  Round 
Alpha  there  is  a  remarkable  arrangement  of  the  stars, 
and  round  Gamma  there  is  one  equally  striking.  Beta 
is  a  magnificent  double,  seen  to  advantage  in  a  2-inch 
telescope  ;  the  component  stars  are  yellow  and  blue.  It 
is  interesting  to  identify  the  faint  stars.  One  of  these, 
6l  Cygni,  is  easily  visible  to  the  unaided  eye.  The  con- 
stellation's most  striking  feature  is  the  long  cross  formed 
by  the  stars  Alpha,  Beta,  Gamma,  Delta,  and  Epsilon. 
Of  these  Alpha  is  the  brightest  and  Beta  the  faintest. 

Draco. — A  long,  straggling  northern  constellation.  It  does 
not  offer  many  attractions  to  the  beginner. 

Eridanus. — Another  straggling  group  seen  in  the  South  in 
winter.  Its  brightest  star  is  invisible  in  the  northern 
hemisphere. 

Gemini. — This  is  a  very  fine  group  easily  identified.  Its 
brightest  stars  are  Pollux  of  the  first  magnitude  and 
Castor  of  the  second.  A  little  north  of  Eta  is  a  star 
cluster  just  visible  to  the  unaided  eye.  Zeta  is  a  well- 
known  variable  easily  within  the  reach  of  the  beginner. 

Hercules. — The  chief  feature  of  this  group  is  the  famous  star 
cluster.  It  is  fairly  well  seen  in  a  2-inch  telescope. 

Hydra. — Like  Draco  and  Eridanus  this  is  a  straggling  group. 
In  the  words  of  Mr.  Maunder  it  "  begins  close  to  Procyon 
under  Cancer,  and  it  stretches  below  the  Zodiacal  con- 
stellations of  Cancer,  Leo,  and  Virgo  and  the  greater 
part  of  Libra.  It  has  few  bright  stars  and  these  grouped 
in  easily  remembered  figures ;  and  the  great  reaches  of 
arren  sky  it  includes  seem  referred  to  in  the  name 
given  to  its  brightest  star,  Al  Fard,  the  solitary." 

Leo. — This  is  a  Zodiacal  constellation  easily  identified.  Its 
brightest  stars  are  Regulus  of  the  first  magnitude  and 
Deiiebola  of  the  second.  Its  most  notable  feature  is  the 
well-known  Regulus.  In  this  constellation  is  the  radiant 
point  of  the  November  meteors. 

Libra. — A  Zodiacal  constellation,  but  very  inconspicuous. 

258 


HOW  TO   KNOW   THE   STARS 

Lyra. — One  of  the  most  compact  and  easily  identified  groups. 
Vega  is  the  brightest  star  and  a  striking  object.  Beta 
is  a  well-known  variable  and  easily  followed  by  the 
unaided  eye. 

Ophiuchus  and  Serpens. — These  two  groups  are  so  intermixed 
that  they  may  be  treated  as  one.  They  are  among  the 
most  difficult  of  all  the  constellations  in  the  en  tire  heavens. 
Serpens  presents  some  good  binocular  fields. 

Orion. — By  common  consent  Orion  is  the  most  magnificent 
of  all  the  constellations.  Betelgeux  and  Rigel  are  the 
two  chief  stars.  Rigel  is  generally  the  brighter,  but 
Betelgeux  is  a  variable  and  at  times  surpasses  Rigel.  The 
red  tint  of  Betelgeux  is  very  noticeable  and  contrasts 
with  the  bluish  white  light  of  Rigel.  The  great  nebula 
in  Orion  is  just  visible  to  the  unaided  eye.  A  binocular 
shows  it,  and  it  is  seen  to  advantage  in  a  2-inch 
telescope,  through  which  it  is  a  striking  and  awe-in- 
spiring spectacle.  Orion  has  two  stars  of  the  first 
magnitude,  Alpha  and  Beta  (Betelgeux  and  Rigel),  and 
five  of  the  second,  Gamma,  Kappa,  Delta,  Epsilon,  and 
Zeta.  The  three  latter  forming  the  "  belt  of  Orion." 

Pegasus. — This  is  a  very  notable  constellation  and  a  con- 
spicuous feature  of  the  autumn  skies.  The  "  Great 
Square  "  is  formed  by  four  stars,  one  of  which,  however, 
belongs  to  the  neighbouring  constellation  Andromeda. 
The  square  is  all  the  more  striking  on  account  of  the 
dearth  of  stars  within. 

Perseus. — To  the  beginner  Perseus  is  perhaps  the  most  interest- 
ing' constellation.  The  brightest  star,  Alpha  (Mirfak), 
is  situated  in  a  magnificent  region.  Seen  with  the  field- 
glass,  there  is  a  curve  of  stars  with  Mirfak  at  the  centre. 
Seen  with  the  telescope,  the  scene  is  even  more  striking. 
Near  to  the  star  Chi  Persei  is  a  magnificent  cluster, 
which  can  be  seen  with  the  binocular,  and  is  a  magnificent 
object  in  a  2-inch  telescope.  Beta  Persei,  or  Algol,  is  one 
of  the  most  remarkable  variable  stars  in  the  sky.  All 
the  variations  are  within  reach  of  the  unaided  eye. 

Pisces. — This  is  a  constellation  of  faint  stars,  of  little  interest 
to  the  beginner. 

Piscis  Australis. — This  constellation  may  just  be  glimpsed  on 
a  clear  autumn  night,  when  the  brightest  star  Fomalhaut 
of  the  first  magnitude  is  to  be  seen  glimmering  on  the 
horizon. 

259 


HOW  TO   KNOW   THE   STARS 

Sagittarius. — A  star  group  deeply  immersed  in  the  Galaxy 
which  well  repays  observation  with  the  binocular. 

Taurus. — This  is  a  constellation  of  the  utmost  charm  and 
beauty.  In  a  field-glass  its  beauties  are  specially  evident. 
The  cluster  of  the  Pleiades  is  particularly  striking  in  a 
binocular,  as  is  also  the  Hyades,  the  group  surrounding 
Aldebaran  (Alpha  Tauri),  the  brilliant  red  star. 

Of  these  two  clusters  the  Pleiades  is  by  far  the  finest. 
Six  stars  are  to  be  seen  by  persons  of  average  eyesight, 
but  with  a  binocular  many  more  are  to  be  counted. 

Ursa  Major. — This  famous  constellation  is  known  to  all,  at 
least  its  chief  stars  which  form  the  Plough.  The  stars 
Alpha,  Beta,  Gamma,  Epsilon,  /eta,  and  Eta  are  of  the 
second  magnitude,  and  Delta  of  the  fourth,  /eta  is 
a  double  easily  seen  with  the  unaided  eye.  The  two  stars 
are  known  as  Mizar  and  Alcor.  In  a  small  telescope 
it  is  a  striking  spectacle. 

Ursa  Minor. — This  group  is  notable  as  it  contains  the  Pole 
Star  of  the  second  magnitude. 

J'irgo. — A  conspicuous  constellation  visible  in  spring.  It  is 
shaped  like  the  letter  V.  Spica,  the  brightest  star,  is  of 
the  first  magnitude. 

Very  little  can  be  done  in  the  study  of  the  planets  with 
the  unaided  eye  or  the  binocular  ;  but  the  phases  of  Venus, 
the  satellites  of  Jupiter,  and  the  mountains  of  the  Moon 
are  all  within  reach  of  a  small  telescope  of  one  or  two 
inches  in  diameter. 


260 


CHAPTER   XXVIII 

TELESCOPES   AND   OBSERVATORIES 

'  I  AHE  greater  part  of  our  knowledge  of  the  science  of 
astronomy  is  due  to  the  marvellous  instrument 
known  as  the  telescope,  which,  by  magnifying  the 
celestial  bodies,  enables  men  to  study  them  at  much  less 
than  their  actual  distance.  Before  the  invention  of  the 
telescope  there  was  certainly  a  science  of  astronomy,  but 
it  was  chiefly  a  science  of  statistics — star-catalogues, 
star-positions,  planetary  positions,  and  apparent  motions. 
Nothing  was  known  of  the  surface  of  the  Moon,  although 
it  lies  so  close  to  us.  Without  the  telescope  mankind 
would  have  remained  in  comparative  ignorance  of  the  outer 
Universe.  Is  it  wonderful,  then,  that  John  Kepler  ad- 
dressed the  newly-invented  instrument  in  these  words : 
"  O  !  telescope,  instrument  of  much  knowledge,  more  pre- 
cious than  any  sceptre.  Is  not  he  who  holds  thee  in  his 
hand  made  king  and  lord  of  the  works  of  God  ?  " 

Telescopes  are  of  two  kinds — the  refracting  telescope, 
the  most  familiar,  and  the  reflecting  telescope.  Of  these 
the  refractor  was  the  first  to  be  invented.  The  first  tele- 
scope was  constructed  in  1609  at  Midclelburg,  in  Holland, 
by  an  optician  named  Lippershey.  The  news  of  the  con- 
struction of  the  first  telescope  reached  Italy  in  the  summer 
of  1609,  when  the  idea  of  constructing  one  presented  itself 
to  the  fertile  mind  of  Galileo.  In  a  letter,  dated  August 
1609,  Galileo  wrote:  "About  two  months  ago  a  report 
was  spread  here — in  Padua — that  in  Flanders  a  spy -glass 
had  been  presented  to  Prince  Maurice,  so  ingeniously  con- 


TELESCOPES   AND   OBSERVATORIES 

structed  that  it  made  most  distant  objects  appear  quite 
near,  so  that  a  man  could  be  seen  quite  plainly  at  a  dis- 
tance of  two  miles.  This  result  seemed  to  me  so  extra- 
ordinary that  it  set  me  thinking,  and  as  it  appeared  to 
me  that  it  depended  upon  the  laws  of  perspective,  I  re- 
flected on  the  manner  of  constructing  it,  and  was  at  length 
so  entirely  successful  that  I  made  a  spy-glass  which  far 
surpasses  the  report  of  the  Flanders  one.  The  effect  of 
my  instrument  is  such  that  it  makes  an  object  fifty  miles 
off'  appear  as  large  as  if  it  were  only  five." 

Such  were  the  humble  beginnings  of  the  telescope,  the 
instrument  which  has  revolutionised  the  science  of  astro- 
nomy. Galileo  constructed  a  number  of  telescopes.  The 
first  was  of  little  scientific  value.  The  second  was  more 
useful,  and  with  the  third  he  commenced  his  observations 
on  the  Moon.  With  his  fifth  instrument  he  discovered 
the  satellites  of  Jupiter. 

The  principle  of  the  Galilean  telescope  is  very  simple. 
It  is  the  simplest  form  of  refractor  through  which  the  ob- 
server looks  directly  at  the  object  of  observation.  The 
object-glass,  or  large  glass  at  the  end,  was,  in  the  Galilean 
telescope,  a  simple  convex  lens.  After  Galileo's  time  larger 
telescopes  were  constructed,  but  they  were  practically 
worthless,  owing  to  a  difficulty  of  construction  which  for 
a  time  seemed  insurmountable.  Owing  to  the  dispersion 
of  light  (the  principles  of  which  cannot  be  explained  in  a 
work  like  the  present)  the  image  of  the  object  was  not 
well  shown,  the  edges  having  fringes  round  them  similar 
to  the  colours  of  the  rainbow.  This  phenomenon,  known 
as  chromatic  aberration,  increased  as  the  object-glasses 
increased  in  size.  For  some  time,  indeed,  astronomers  en- 
deavoured to  surmount  the  difficulty  by  making  telescopes 
immensely  long.  Huyghens,  Bianchini,  and  Cassini,  astro- 


TELESCOPES   AND   OBSERVATORIES 

nomers  of  the  seventeenth  century,  constructed  telescopes 
over  a  hundred  feet  in  length.  They  were  very  unwieldy, 
and  little  scientific  work  of  importance  was  accomplished 
by  means  of  them.  Thus,  no  effective  antidote  had  been 
found  for  the  chromatic  aberration.  Accordingly,  Sir 
Isaac  Newton,  who  devoted  much  attention  to  the  subject, 
came  to  the  conclusion  that  it  was  impossible  to  construct 
a  refracting  telescope  which  would  be  free  from  this  defect. 
The  same  view  was  reached  about  the  same  time  by  the 
Scottish  astronomer,  James  Gregory.  Both  Newton  and 
Gregory  agreed  in  condemning  the  refractor,  and  both 
commenced  to  devise  a  new  form  of  telescope. 

The  form  of  telescope  devised  by  them  was  the  reflector, 
an  instrument  formed  on  the  principle  of  the  reflection 
of  light.  In  this  form  of  telescope  the  light  coming 
into  the  telescope  from  the  object  to  be  observed  was 
reflected  into  the  eyepiece  from  the  surface  of  a  concave 
mirror  constructed  of  the  alloy  known  as  speculum 
metal.  Gregory  and  Newton  constructed  instruments 
which,  while  similar  in  principle,  differed  slightly  in 
detail.  One  of  the  drawbacks  of  the  reflector  is  that 
a  second  reflection  is  necessary  before  the  rays  from  the 
object  under  observation  can  enter  the  eyepiece.  If  the 
observer  looked  down  the  tube  of  the  telescope  at  the 
image,  he  would  at  once  cut  off  the  light  from  the  object 
he  wished  to  observe.  Newton  therefore  in  his  telescope 
placed  the  eyepiece  in  the  side,  and  into  it  the  rays  were 
deflected  by  a  second  reflection.  Gregory,  on  the  other 
hand,  put  the  eyepiece  immediately  behind  the  principal 
mirror.  The  Newtonian  form  is  the  one  most  used. 
•*  After  Newton's  invention,  the  reflecting  telescope  became 
very  popular.  Its  chief  development  was  due  to  Sir  William 
Herschel,  who  gave  it  immense  popularity.  It  is  a  remark - 

263 


TELESCOPES   AND   OBSERVATORIES 

able  illustration  of  the  sequence  of  events  that  Herschel's 
development  of  the  reflecting  telescope  was  due  to  the  fact 
that  he  was  at  first  an  amateur  astronomer,  who  was  obliged 
to  make  his  own  telescope.  He  constructed  many  reflec- 
tors and  devised  a  modification  of  the  Newtonian  form, 
known  as  the  Herschelian.  In  1775,  Herschel  constructed 
his  seven-foot  telescope,  and,  after  making  instruments  of 
ten,  twenty,  and  thirty  feet  in  focal  length,  he  constructed 
in  1 789  the  famous  forty-foot  reflector  with  which  he  dis- 
covered the  inner  satellites  of  Saturn. 

In  the  hands  of  Herschel,  the  reflecting  telescope  seemed 
to  exhaust  its  possibilities,  and  men  began  to  turn  their 
attention  to  the  despised  refractor.  In  the  eighteenth 
century  it  was  found  to  be  possible  by  combining  lenses 
of  flint  and  crown  glass  in  the  object-glasses  of  refractors 
to  practically  eliminate  the  "aberration"  which  had  put  a 
check  on  the  advance  of  the  refracting  telescope.  For  some 
time  it  was  found  difficult  to  procure  object-glasses  of  flint 
glass  of  sufficient  size  to  make  any  considerable  advance 
in  telescope-construction.  However,  in  the  hands  of  a  firm 
of  Swiss  opticians  remarkable  progress  was  made,  and  in 
1823  a  lens  of  12  inches  diameter  was  successfully  finished. 

Meanwhile,  the  greatest  development  of  the  reflecting 
telescope  was  soon  reached.  Most  people  have  heard  of 
Lord  Rosse's  telescope.  It  is,  in  point  of  size,  about  the 
largest  telescope  in  the  world,  although  its  situation  in  the 
unfavourable  climate  of  Ireland  has  rendered  it  practically 
useless  within  recent  years.  The  history  of  this  telescope 
is  so  interesting  that  it  is  worth  giving  at  some  length. 
When  quite  a  young  man,  the  third  Earl  of  Rosse  con- 
ceived the  idea  of  erecting  the  largest  telescope  in  the 
world  on  his  estate  in  Ireland.  Being  an  amateur,  he 
turned  his  attention  to  the  reflecting  telescope.  As  the 


Ax  WORK  IN  GREENWICH  OBSERVATORY 

This  plate  shows  astronomers  at  Greenwich  observing  the  planet  Mars  at  its 
appearance  in  1909.  The  room  is  quite  dark  except  for  the  light  which  comes  in 
from  the  night  sky  and  the  electric  lamp  by  means  of  which  one  of  the  observers 
takes  down  his  nutes. 


TELESCOPES   AND   OBSERVATORIES 

late  Miss  Clerke  points  out :  "  He  had  to  rely  entirely  on 
his  own  invention  and  to  earn  his  own  experience.  He 
had  no  skilled  workmen  to  assist  him.  His  implements, 
both  animate  and  inanimate,  had  to  be  formed  by  himself. 
Peasants  taken  from  the  plough  were  educated  by  him 
into  efficient  mechanics  and  engineers."  In  1827  he  began 
work,  and  it  was  not  until  April  1842,  fifteen  years  later, 
that  he  succeeded  in  constructing  the  famous  mirror,  six 
feet  in  diameter,  with  which  he  was  to  survey  the  heavens. 
By  February  1845  the  telescope  was  ready  for  work. 

A  tube,  which  resembled  when  erect  one  of  the  ancient 
round  towers  of  Ireland,  served  as  the  habitation  of  the 
great  mirror.  The  tube  was  no  less  than  fifty-eight  feet 
long  and  seven  feet  in  diameter,  so  that  when  it  was 
horizontal  a  man  of  considerable  height  could  walk  through 
it  holding  an  umbrella.  Sir  Robert  Ball,  who  for  some 
years  had  charge  of  the  great  telescope,  has  the  following 
interesting  description  of  the  instrument : — 

"  Almost  the  first  point  which  would  strike  the  visitor  to 
Lord  Rosse's  telescope  is  that  the  instrument  at  which  he  is 
looking  is  not  only  enormously  greater  than  anything  of  the 
kind  that  he  has  ever  seen  before,  but  also  that  it  is  some- 
thing of  a  totally  different  nature.  In  an  ordinary  telescope 
he  is  accustomed  to  find  a  tube  with  lenses  of  glass  at  either 
end,  while  the  large  telescopes  that  we  see  in  our  Observa- 
tories are  also  in  general  constructed  on  the  same  principle. 
At  one  end  there  is  the  object-glass,  and  at  the  other  end 
the  eyepiece,  and  of  course  it  is  obvious  that  with  an  in- 
strument of  this  construction  it  is  to  the  lower  end  of  the 
tube  that  the  eye  of  the  observer  must  be  placed  when 
the  telescope  is  pointed  to  the  skies.  But  in  Lord  Rosse's 
telescope  you  would  look  in  vain  for  these  glasses,  and  it  is 
not  at  the  lower  end  of  the  instrument  that  you  are  to  take 
your  station  when  you  are  going  to  make  your  observations. 
The  astronomer  at  Parsonstown  has  rather  to  avail  himself  of 
the  ingenious  system  of  staircases  and  galleries  by  which  he 
is  enabled  to  obtain  access  to  the  mouth  of  the  great  tube.'' 

265 


TELESCOPES   AND   OBSERVATORIES 

Many  valuable  observations  and  discoveries  were  made 
by  means  of  the  Rosse  telescope  during  the  first  few  years 
of  its  existence,  but  it  was  not  long  before  its  powers 
began  to  deteriorate.  Its  situation  in  the  unfavourable 
climate  of  Ireland  greatly  injured  its  usefulness,  and  it  is 
now  little  more  than  an  astronomical  curiosity.  It  had 
only  a  few  brilliant  years  of  investigation  and  discovery. 
About  the  time  the  Rosse  telescope  was  erected,  a  new 
material  for  the  construction  of  reflecting  telescopes  was 
invented  by  two  independent  French  investigators — glass 
upon  which  a  thin  film  of  silver  is  deposited.  These  in- 
struments have  a  light-gathering  power  far  exceeding  the 
telescopes  whose  mirrors  are  constructed  of  speculum  metal. 

In  June  1847  there  was  erected  the  famous  Harvard 
refracting  telescope  of  15  inches  aperture.  This  was  the 
beginning  of  the  development  of  the  refractor.  A 
23-inch  telescope  on  the  same  lines  was  constructed  by  a 
self-taught  English  optician  in  1868;  while  a  year  or  two 
later  another  self-taught  optician,  in  America,  followed 
with  the  construction  of  the  famous  26-inch  telescope  of 
the  Washington  Observatory,  rendered  famous  by  the  dis- 
covery by  the  late  Professor  Hall,  when  using  it,  of  the 
satellites  of  Mars.  Next  in  the  eighties  came  the  erection 
of  telescopes  of  29|  inches  and  30  inches  aperture  respec- 
tively for  the  Observatories  of  Nice  in  France,  and  Pulkowa 
in  Russia.  The  30-inch  telescope  of  the  Russian  National 
Observatory  was  for  some  years  the  greatest  refracting 
telescope  in  the  world.  But  it  did  not  retain  this  position 
for  long.  As  one  writer  puts  it :  "  The  Czar  of  all  the 
Russias  was  outbidden  twice  by  American  millionaires.11 

The  first  of  these  was  James  Lick,  whose  name  is  now 
immortalised  in  connection  with  the  great  Observatory  in 
California,  where  so  many  great  discoveries  have  been 

266 


TELESCOPES   AND   OBSERVATORIES 

made.  The  story  goes  that  Mr.  Lick,  a  Californian 
millionaire,  being  very  desirous  of  erecting  a  permanent 
memorial  of  himself  and  his  wife,  proposed  to  leave  money 
for  the  erection  of  two  immense  statues  on  the  Pacific 
coast.  About  this  time,  however,  an  astronomer  suggested 
that,  in  case  of  war,  such  statues  would  be  liable  to  de- 
struction by  the  enemy,  and  that  a  great  telescope  erected 
on  one  of  the  mountains  in  California  would  be  much 
safer.  Accordingly  Lick  took  up  with  much  enthusiasm 
the  erection  of  a  gigantic  telescope,  making  it  a  condition, 
however,  that  his  remains  were  to  be  interred  below  the 
base  of  the  instrument.  He  died  many  years  before  the 
Observatory  was  completed. 

The  late  Professor  Newcomb  remarks  that  the  erection 
of  an  Observatory  was  not  in  the  millionaire's  mind ;  all 
he  wanted  was  a  gigantic  telescope.  "  From  his  point  of 
view,  as,  indeed,  from  that  of  the  public  very  generally, 
the  question  of  telescopic  vision  is  merely  one  of  magni- 
fying power." 

An  Observatory  was,  however,  necessary  in  order  to 
afford  a  house  for  the  great  telescope ;  but  the  idea  of 
having  the  most  powerful  refracting  telescope  in  the 
world  was  kept  in  view,  and  at  last  an  object  glass  36 
inches  in  diameter  was  constructed.  The  Observatory 
was  placed  on  Mount  Hamilton,  a  lonely  elevation  4250 
feet  in  height,  in  California,  amid  the  purest  air,  where 
a  large  instrument  could  be  used  to  advantage.  In  1888 
the  Observatory  was  finished,  and  the  great  Lick  telescope 
entered  on  a  long  career  of  usefulness.  Unlike  the  mag- 
nificent telescope  of  Lord  Rosse,  ruined  by  its  situation  in 
a  poor  climate,  the  great  Lick  telescope  is  still  in  the 
prime  of  its  life.  The  discovery  of  new  double  stars,  of 
a  new  satellite  of  Jupiter,  the  measurements  of  nebular 

267 


TELESCOPES   AND   OBSERVATORIES 

motion,  within  a  few  years  of  the  erection  of  the  telescope, 
is  a  testimony  not  only  to  the  excellence  of  the  instru- 
ments but  the  skill  of  the  observers — men  such  as  Pro- 
fessors Burnham,  Barnard,  Keeler,  and  Campbell,  whose 
names  are  deservedly  famous  in  astronomy.  The  colony 
of  astronomers  on  Mount  Hamilton  is  isolated  from  the 
rest  of  the  world,  and  it  requires  a  considerable  amount 
of  self-sacrifice  to  pursue  astronomy  under  such  conditions. 
"To  those  in  actual  charge  of  the  telescope,"  says  a 
well-known  astronomer,  "  the  situation  is  not  without  its 
disadvantages.  They  are  at  some  distance  from  the 
town,  and  without  many  of  the  comforts  of  civilisation. 
The  winter  on  the  mountain  is  severe,  and  brings  with 
it  at  times  considerable  privations.  In  one  winter  there 
was  actually  no  water  to  drink  except  what  had  passed 
through  the  engines. " 

The  great  Lick  telescope  enjoyed  for  about  ten  years 
the  place  of  the  greatest  telescope  in  the  world.  At 
length  Mr.  Yerkes,  another  millionaire,  gave  to  the 
University  of  Chicago  money  to  equip  an  Observatory  and 
erect  a  telescope  40  inches  in  aperture,  four  inches  greater 
than  the  Lick  telescope.  This  great  telescope  was  set 
up  in  1898  at  the  new  Observatory  of  the  University  of 
Chicago,  Williams  Bay,  Wisconsin,  eighty  miles  from 
Chicago.  Here  it  is  in  the  hands  of  expert  observers. 

Foremost  among  other  astronomical  institutions  in 
America  must  be  placed  the  Carnegie  Observatory,  on 
Mount  Wilson,  California.  Dr.  Andrew  Carnegie,  unlike 
Messrs.  Lick  and  Yerkes,  is  deeply  interested  in  all 
things  scientific,  and  his  munificent  donations  to  the 
Carnegie  Institute  have  conferred  inestimable  benefits  on 
astronomy  and  astronomers.  In  1905  the  Carnegie  Ob- 
servatory on  Mount  Wilson  was  founded,  and  at  its  head 

268 


TELESCOPES   AND   OBSERVATORIES 

was  placed  Professor  Hale,  one  of  the  most  distinguished 
astronomers  of  the  United  States.  Among  the  instru- 
ments erected  here  are  the  60-inch  reflector,  with  which 
much  important  work  has  been  done,  while  greater  things 
are  expected  from  the  100-inch  silver-on-glass  reflector, 
which  surpasses  Lord  Rosse's  famous  telescope  in  point  of 
size.  Like  the  Lick  Observatory,  the  Carnegie  Obser- 
vatory is  isolated  from  civilisation,  and  it  is  a  matter  of 
self-sacrifice  to  be  an  astronomer  on  Mount  Wilson. 

The  view  that  a  clear  atmosphere  is  essential  to  good 
astronomical  work  has  been  maintained  for  many  years  by 
Professor  Percival  Lowell,  who  established  in  1894  the 
now  famous  Lowell  Observatory  at  Flagstaff',  Arizona. 
Here  he  erected  his  18-inch  and  24-inch  refractors,  which 
he  claims  to  be  almost  unrivalled  for  space-penetrating 
power,  and  here  also  he  proposes  to  erect  a  40-inch  re- 
flector for  photographic  purposes.  Work  amid  surround- 
ings so  far  removed  from  human  habitation  entails,  as  we 
remarked,  a  good  deal  of  self-sacrifice,  but,  as  indicated  by 
Professor  Lowell's  remarks,  it  seems  to  have  also  a  certain 
charm  :  "  To  sally  forth  into  the  untrod  wilderness  in  the 
cold  and  dark  of  a  winter's  small  hours  of  the  morning, 
with  the  snow  feet  deep  upon  the  ground  and  the  frosty 
stars  for  mute  companionship,  is  almost  to  forget  one's 
self  a  man  for  the  solemn  awe  of  one's  surroundings. 
Fitting  portal  to  communion  with  another  world,  it  is 
through  such  avenue  one  enters  on  his  quest,  where  the 
common  and  familiar  no  longer  jostle  the  unknown  and 
strange." 

The  Harvard  College  Observatory  in  Massachusetts  has 
none  of  the  advantages  of  the  great  institutions  already 
named,  so  far  as  climate  is  concerned ;  yet  it  has  a 
reputation  and  a  record  second  to  none.  Professor 

269 


TELESCOPES   AND   OBSERVATORIES 

E.  C.  Pickering,  director  of  the  Observatory,  has  raised 
the  institution  to  a  high  standard  of  efficiency.  Photo- 
graphic work  is  one  of  the  specialities  of  the  Observatory. 
He  charts  the  sky  once  a  month  ;  with  a  smaller  instrument, 
and  on  a  smaller  scale,  he  charts  the  brighter  stars  every 
fine  night,  so  that  if  a  star  brighter  than  the  sixth  magni- 
tude makes  its  appearance  in  any  part  of  the  heavens, 
he  would  have  a  record  of  it  on  the  first  clear  evening. 

Turning  from  the  great  institutions  of  the  New  World  to 
the  more  historically  interesting  Observatories  of  the  Old,  we 
find  two — Greenwich  Observatory  and  Paris  Observatory— 
which  have  the  greatest  historical  interest  in  the  world. 
The  Paris  Observatory  was  erected  a  few  years  before  the 
sister  institution,  being  completed  in  1671.  Four  years 
later  was  laid  the  foundation -stone  of  the  Royal  Observatory 
at  Greenwich,  of  which  the  famous  John  Flamsteed  was 
made  director,  with  the  title  of  Astronomer  Royal.  It  is 
not  too  much  to  say  that  the  science  of  practical  astronomy 
was  founded  at  Greenwich.  The  work  of  Bradley,  the 
third  Astronomer  Royal,  forms  an  epoch  in  the  history 
of  astronomy.  The  history  of  this  great  and  honourable 
institution  would  take  too  long  to  record  here.  The  object 
for  which  the  Observatory  was  founded — practical  astronomy 
— is  still  regarded  as  the  chief  side  of  the  work,  and  for 
this  a  large  instrument  is  not  required.  Still  Greenwich  is 
at  the  same  time  thoroughly  progressive,  and  a  good  deal 
of  photographic  and  observational  work  is  done.  The  Obser- 
vatory boasts  a  2 8 -inch  refractor,  a  very  fine  instrument. 

The  Paris  Observatory  is  also  deservedly  famous,  having 
been  presided  over  by  a  succession  of  famous  men,  who 
have  done  much  for  the  development  of  astronomy. 
These  two  Observatories  occupy  the  chief  places  among 
the  institutions  in  Europe  for  the  cultivation  of  astronomy. 

270 


TELESCOPES   AND   OBSERVATORIES 

Other  famous  Observatories  in  Europe  include  Edinburgh, 
Potsdam,  Pulkowa,  Heidelberg,  Milan,  and  Rome. 

The  Edinburgh  Observatory  was  founded  in  1776 — a 
century  after  the  Greenwich  Observatory — and  was  origi- 
nally the  property  of  the  Astronomical  Institution  of 
Edinburgh,  being  erected  for  the  convenience  of  members 
of  the  institution  who  wished  to  make  practical  observa- 
tions. It  was  enlarged  in  1811,  and  with  its  instruments 
the  famous  astronomer  Henderson,  who  first  measured  the 
distances  of  the  stars,  made  his  earliest  observations.  In 
1854  the  Observatory,  which  occupied  a  fine  position  on 
the  Calton  Hill,  Edinburgh,  became  Government  property. 
It  was  converted  into  a  Royal  Observatory,  and  at  its  head 
was  placed  Thomas  Henderson,  Professor  of  Astronomy 
in  the  University  of  Edinburgh,  who  became  Astronomer 
Royal  of  Scotland.  In  1896  a  new  Royal  Observatory 
was  erected  on  Blackford  Hill,  in  the  outskirts  of  the  city, 
away  from  the  smoke  of  the  city.  The  new  institution  is 
second  only  to  Greenwich  among  British  Observatories. 
The  old  Observatory  buildings  on  the  Calton  Hill  were 
acquired  by  Edinburgh  Town  Council.  The  Council  con- 
verted them  into  a  City  Observatory,  mainly  for  educa- 
tional purposes.  It,  however,  possesses  the  largest  telescope 
in  Scotland,  a  22-inch  refractor. 

The  Observatory  at  Potsdam  is  equipped  with  a  magni- 
ficent 28-inch  refractor.  This  institution  is  known  as 
an  "  Astrophysical  Observatory,"  because  the  new  side 
of  astronomy — the  study  of  astrophysics,  the  physical  in- 
vestigation of  the  heavenly  bodies — is  chiefly  pursued  there, 
^he  Observatory  was  founded  in  1874,  and  was  the  scene 
of  the  labours  of  the  great  German  astronomer  Vogel. 

Pulkowa  Observatory  was  founded  in  1835  by  the  Czar 
of  Russia.  It  was  equipped  with  what  was  then  one  of  the 

271 


TELESCOPES   AND   OBSERVATORIES 

greatest  telescopes  in  the  world,  while  one  of  the  most 
famous  astronomers,  William  Struve,  the  German  observer, 
was  placed  at  its  head.  In  1884,  under  his  son  and 
successor,  Otto  Struve,  the  Observatory  was  furnished  with 
what  was  at  that  time  the  greatest  telescope  in  the  world. 
It  is  now,  however,  much  behind  the  American  Observatories 
in  point  of  the  size  of  its  telescopes.  It  has  been  directed 
by  a  succession  of  very  able  astronomers. 

The  Heidelberg  Observatory  is  of  no  great  antiquity, 
but  its  record  is  a  noble  one.  It  was  erected  in  1893,  and 
at  its  head  was  placed  Professor  Max  Wolf,  the  great 
astronomical  photographer.  Here  was  erected  the  famous 
photographic  telescope  by  means  of  which  Dr.  Wolf  has 
secured  his  beautiful  photographs. 

The  Italian  Observatories  of  Milan  and  Rome  are 
famous  chiefly  from  the  historical  interest  which  attaches 
to  them.  The  Brera  Observatory  in  Milan  was  the  scene 
of  the  work  of  Professor  Schiaparelli  for  upwards  of  forty 
years.  Favoured  with  a  magnificent  sky  and  a  fair-sized 
instrument,  Schiaparelli  certainly  made  the  most  of  his  op- 
portunities. The  Observatory  of  Rome  was  the  scene  of  the 
labours  of  the  two  distinguished  men  Secchi  and  Tacchini, 
who,  favoured  by  the  beautiful  climate  of  Italy,  were  also  en- 
abled to  make  the  most  of  their  opportunities  in  a  different 
field  of  astronomical  research — solar  and  stellar  physics. 

Among  the  Observatories  in  the  southern  hemisphere 
three  may  be  mentioned  specially — the  Cape  Observatory, 
the  scene  of  the  work  of  Thomas  Henderson  and  more 
recently  of  Sir  David  Gill ;  the  Cordova  Observatory  in 
Argentina ;  and  the  Observatory  at  Arequipa  in  Peru. 
The  last  named  is  the  southern  observing  station  of 
Harvard  College  Observatory,  which  thus  surveys  both 
hemispheres  of  the  sky. 

272 

r-.  • 
\    •  M  . 


CHAPTER   XXIX 

THE   ROMANCE   OF   DISCOVERY:    THE 
EARLY  ASTRONOMERS 

IN  the  previous  chapters,  reference  has  been  made  to 
the  vast  amount  of  knowledge  which  has  been 
amassed  by  the  human  race  concerning  the  Universe 
and  the  place  of  our  world  in  Nature.  In  the  early  ages 
of  our  world's  history,  mankind  was  sunk  in  ignorance 
regarding  the  heavenly  bodies,  as  was  clearly  shown  in 
the  opening  chapter.  To-day  we  have  acquired  a  con- 
siderable insight  into  the  system  of  the  Universe  at  the 
present  time,  and  have  even  dared  to  attempt  to  read  the 
past  of  the  Universe  and  to  trace  its  future.  The  advance 
of  astronomy  throughout  the  ages  has  been  like  that 
of  a  mighty  army  marching  to  victory.  The  march  has 
been  a  triumphal  progress  so  far,  but  we  are  no  nearer 
the  end,  for  as  soon  as  one  stage  of  the  journey  is  reached, 
new  and  unfathomable  vistas  come  into  view. 

Carlyle  has  remarked  that  the  history  of  the  world  is 
the  history  of  its  great  men  ;  and  it  is  equally  true  to 
say  that  the  history  of  astronomy  is  the  life-story  of 
astronomers.  Of  these  the  earliest  are  lost  in  the  mists 
of  antiquity,  and  the  name  of  the  first  astronomer  will 
probably  remain  for  ever  unknown.  In  the  early  ages, 
students  of  the  heavens  were  not  merely  astronomers. 
Thus,  Aristotle,  who  exercised  so  profound  an  influence 
on  astronomy,  was  an  all-round  scientist  and  philosopher. 
The  first  astronomer,  in  the  actual  sense  of  the  word,  was 

273  s 


THE   EARLY   ASTRONOMERS 

Hipparchus.  He  was  born  about  170  B.O.  He  con- 
structed a  catalogue  of  the  positions  of  the  stars,  an  idea 
supposed  to  have  been  suggested  by  the  appearance  of  a 
temporary  star.  Hipparchus  died  about  120  n.r.  Over 
two  hundred  years  later,  Ptolemy  described  him  as  a 
"  most  truth-loving  and  labour-loving  man." 

One  of  the  most  famous  of  the  ancient  astronomers  was 
the  Egyptian,  Claudius  Ptolemy,  who  is  supposed  to 
have  lived  at  Alexandria  between  about  A.D.  127  and  157. 
Ptolemy's  ideas  of  the  Universe  were  believed  for  fourteen 
hundred  years,  and  he  propounded  the  famous  "  Ptole- 
maic theory,"  which  was  eventually  upset  by  Copernicus. 
Ptolemy  considered,  like  Aristotle,  that  the  Earth  was 
round  and  immovable.  The  celestial  bodies  were  thought 
to  revolve  round  it  in  the  following  order :  the  Moon, 
Mercury,  Venus,  the  Sun,  Mars,  Jupiter,  Saturn,  and  the 
stars  proper.  The  planets  were  believed  to  revolve  in 
circles  round  imaginary  centres,  which  revolved  in  circles 
round  the  Earth.  This  theory  was  preserved  in  Ptolemy's 
great  work,  "  The  Almagest." 

After  the  death  of  Ptolemy  the  science  of  astronomy 
was  taken  up  by  the  Arabians,  the  chief  of  these  being 
Ulugh  Beg,  King  of  Samarcand,  who  lived  in  the  fifteenth 
century.  He  made  a  catalogue  of  the  stars  more  perfect 
than  that  of  Hipparchus,  and  it  remained  the  finest  until 
the  days  of  Tycho  Brahe.  Ulugh  Beg  was  assassinated 
by  his  son,  who  desired  the  throne,  in  1447,  twenty- 
six  years  before  Copernicus  was  born.  It  had  become 
plain  even  before  the  time  of  Ulugh  Beg  that  the 
theory  of  Ptolemy  was  very  complicated.  Eventually, 
Alphonso  X.,  King  of  Castile,  who  took  a  great 
interest  in  astronomy,  on  hearing  explained  to  him  the 
Ptolemaic  theory,  declared  that  if  he  had  been  consulted 

274 


THE  EARLY  ASTRONOMERS 

at  the  Creation  he  could  have  given  some  useful  hints. 
This  is  often  considered  to  have  been  an  irreligious 
remark,  but  we  must  remember  that  Alphonso  X.  was 
dissatisfied  with  Ptolemy's  views.  The  ancient  astro- 
nomers ended  with  Ulugh  Beg.  Though  Pythagoras 
had  said  that  the  Earth  moved,  the  end  of  the  fifteenth 
century  found  the  world  more  ignorant  of  astronomy  than 
it  had  been  in  the  time  of  Aristotle  and  Hipparchus. 
Astronomy  was  therefore  prepared  for  the  revolution 
of  Copernicus. 

The  system  of  astronomy  according  to  Aristotle  and 
Ptolemy  was  implicitly  accepted  during  the  Middle  Ages. 
The  Church  of  Rome  contrived  to  make  the  Ptolemaic 
system  agree  with  its  own  particular  interpretation  of  the 
Bible,  and  thus  it  was  that  nobody  thought  of  questioning 
whether  Aristotle  was  right  or  wrong  until  Copernicus 
came  upon  the  scene.  As  has  been  well  said  :  "  All  who 
in  these  days  value  freedom  of  thought,  every  man 
who  now  follows  freely  and  honestly  the  leading  of  the 
mind  and  conscience  God  has  given  him,  owes  no  small 
debt  to  the  old  monk  who,  in  the  solitude  of  the  monas- 
tery garden  at  Frauenburg,  thought  out  the  overthrow 
of  the  authority  of  Aristotle." 

Nicolaus  Copernicus,  the  founder  of  modern  astronomy, 
was  born  at  Thorn,  on  the  Vistula,  in  Poland,  in  1473. 
He  was  the  son  of  a  tradesman  named  Nicolaus  Coper- 
nicus, and  his  uncle  was  a  bishop  in  the  Cathedral  of 
Frauenburg.  It  has  been  pointed  out  as  a  remarkable 
coincidence  that  the  great  astronomer  had  just  reached 
manhood  when  Columbus  discovered  America.  Coper- 
nicus was  educated  at  the  University  of  Cracow,  where  he 
devoted  himself  first  to  medicine  and  philosophy,  and 
afterwards  to  astronomy,  mathematics,  and  painting. 

275 


THE  EARLY  ASTRONOMERS 

After  spending  some  years  in  various  parts  of  Italy, 
Copernicus,  in  1500,  went  to  Rome,  and  was  appointed 
Professor  of  Mathematics.  Here  he  studied  astronomy 
in  earnest,  and  was  universally  acknowledged  to  be  a 
great  man  of  science.  He  did  not  remain  long  in  Rome, 
but  returned  to  Poland,  where  he  settled  at  the  Cathedral 
of  Frauenburg  as  a  priest,  devoting  himself  to  astronomy 
and  to  his  duties  as  an  ecclesiastic.  He  was  of  a  grave 
and  serious  nature,  and  made  only  a  few  intimate  friend- 
ships. 

Early  in  his  career  Copernicus  came  to  doubt  the  truth 
of  the  Ptolemaic  theory  on  account  of  its  complications. 
He  noticed  that  everything  was  done  in  Nature  by  the 
simplest  methods.  Every  new  irregularity  which  was 
discovered  in  the  motions  of  the  planets  required  a  new 
epicycle,  making  the  system  of  Ptolemy  so  complicated 
that  it  could  scarcely  be  understood.  Another  great 
difficulty  which  Copernicus  noticed  was  that  the  stars 
were  represented  as  revolving  round  the  Earth  in  the 
short  space  of  twenty-four  hours.  Some  suggestions  that 
had  been  made  by  the  ancient  Greeks  specially  struck 
him.  Nicetas  had  suggested  the  rotation  of  the  Earth 
on  its  axis  to  account  for  the  diurnal  motion  of  the 
heavens,  a  suggestion  which  Ptolemy  considered  and 
rejected.  Philolaus  thought  that  the  Earth  moved,  and 
not  the  Sun.  These  considerations  led  Copernicus  to 
revolutionise  men's  ideas  of  the  entire  planetary  system. 

The  first  great  discovery  of  Copernicus  was  that  of  the 
rotation  of  the  Earth  on  its  axis.  An  argument  which 
Ptolemy  had  used  in  trying  to  prove  that  the  Earth  did 
not  rotate,  namely,  that  there  would  be  such  a  rush  in  the 
atmosphere  as  would  carry  men  off  the  surface,  Copernicus 
answered  by  showing  that  the  inhabitants  would  be  carried 

276 


THE  EARLY  ASTRONOMERS 

by  the  Earth  in  the  same  manner  as  a  man  carries  his 
overcoat.  Copernicus  also  showed  that  it  was  much  simpler 
for  the  Earth,  along  with  the  other  planets,  to  revolve  round 
the  Sun,  in  an  orbit  between  those  of  Venus  and  Mars, 
than  for  the  Sun  and  planets  to  revolve  round  the  Earth. 
He  also  said  that,  if  his  opinions  were  correct,  Venus  and 
Mercury  should  exhibit  phases  like  the  Moon.  In  the 
case  of  Venus  these  phases  were  discovered  telescopically 
by  Galileo  in  1611,  and  Mercury  was  also  proved  after- 
wards to  show  phases.  In  the  case  of  the  stars  Copernicus 
made  little  advance.  The  absence  of  parallax  on  account 
of  the  Earth's  motion  was  for  long  considered  a  great  draw- 
back to  the  Copernican  theory.  Copernicus  declared  that 
the  distance  of  the  stars  must  be  so  enormous  that  there 
would  be  little  or  no  parallax. 

Copernicus  did  not  at  once  publish  his  great  discoveries. 
Still  his  opinions  were  well  known.  Men  of  science  flocked 
to  Frauenburg  out  of  curiosity  to  know  of  the  new  system, 
and  went  away  convinced  that  it  was  true.  Copernicus' 
friends  had  repeatedly  urged  him  to  have  his  works  pub- 
lished in  book  form,  but  he  refused.  An  event  happened, 
however,  which  caused  him  to  give  his  system  to  the  world. 
A  young -admirer,  George  Joachim,  or  Rheticus,  gave  up  his 
position  as  Professor  of  Mathematics  in  the  University  of 
Wittenberg  in  Germany  in  order  to  go  to  Frauenburg  to 
hear  the  opinions  of  Copernicus.  He  soon  became  con- 
vinced of  the  truth  of  the  Copernican  system.  In  1541, 
when  Copernicus  was  an  old  man  of  sixty-eight,  he  agreed 
to  give  his  book  to  the  world,  and  gave  over  the  care  of 
the  publication  to  Rheticus,  who  had  the  book  printed  at 
Nuremberg  in  Germany,  by  a  man  named  Andrew  Osiander. 
The  great  work,  which  was  entitled  "  De  Revolutionibus 
Orbium  Ccelestium"  was  published  in  1543.  Osiander 

277 


THE  EARLY  ASTRONOMERS 

who  published  it  was  afraid  of  the  opposition  which  it 
would  arouse,  and  wrote  a  preface  to  the  book  saying  that 
the  opinions  of  Copernicus  were  merely  founded  on  theory, 
and  need  not  be  received  as  true.  Copernicus  died  suddenly 
at  the  age  of  seventy,  on  May  23,  1 543.  A  few  hours 
before  his  death  he  received  the  first  copy  of  his  great  work. 
He  was  buried  in  the  Cathedral  of  Frauenburg,  and  no 
mention  of  his  great  discoveries  was  made  on  his  tombstone. 
Not  until  thirty  years  after  his  death  was  any  memorial 
erected  to  his  memory.  When  he  died,  astronomy  was  left 
in  a  most  unsettled  state.  The  tables  of  the  planetary 
motions  predicting  eclipses,  conjunctions,  oppositions, being 
based  on  the  observations  of  the  Greeks  and  the  Arabs, 
were  often  several  hours  or  days  wrong.  It  was  thus  obvious 
that  until  the  motions  of  the  planets  had  been  more  cor- 
rectly investigated,  the  question  of  the  true  system  of  the 
world  must  remain  more  or  less  unsolved. 

Three  years  after  the  death  of  Copernicus,  in  1 546,  there 
was  born  at  Knudstrup,  in  Denmark,  one  who  was  destined 
to  place  astronomy  on  an  entirely  new  basis — that  of  exact 
observation.  His  name  was  Tycho  Brahe.  He  was  the 
eldest  son  of  a  Danish  nobleman,  Otto  Brahe,  and  was 
educated  by  his  uncle,  George  Brahe.  When  he  was 
thirteen  years  of  age  he  was  sent  to  the  University  of 
Copenhagen,  and  an  eclipse  of  the  Sun  which  happened  in 
1560  directed  his  thoughts  to  astronomy.  His  uncle, 
however,  desired  him  to  study  law,  and,  to  take  his 
attention  from  science,  sent  Tycho  to  the  University  of 
Leipzig,  in  Germany.  Dr.  Dreyer,  to  whom  all  interested 
in  astronomy  are  indebted  for  his  admirable  biography  of 
the  great  Danish  astronomer,  informs  us  that  Tycho  was 
accompanied  to  Leipzig  by  a  young  man  named  Vedel,  who 
acted  as  his  tutor.  George  Brahe  had  instructed  Vedel 

278 


THE  EARLY  ASTRONOMERS 

not  to  allow  Tycho  to  continue  studying  astronomy,  which 
in  those  days  was  looked  upon  as  a  waste  of  time,  and  a 
most  undignified  occupation  for  the  son  of  a  nobleman. 
But  Tycho  was  not  to  be  diverted  from  science,  having  no 
interest  whatever  in  the  study  of  law.  He  bought,  unknown 
to  his  tutor,  a  small  celestial  globe  in  order  to  know  how  to 
find  the  stars.  He  could  only  use  it  while  Vedel  was  asleep. 
Tycho's  first  instruments  were  a  pair  of  compasses,  one  leg  of 
which  he  could  point  at  the  object  observed,  and  the  other 
at  some  known  fixed  star,  and  so  could  measure  their  angu- 
lar distance  apart.  By  this  time  Vedel  had  found  that 
Tycho  had  no  interest  in  law.  Tycho's  uncle  died  in 
1565,  and  he  was  free  to  study  the  stars.  His  relatives, 
who  considered  it  a  disgrace  to  study  astronomy,  began 
to  despise  him,  but  nothing  would  now  distract  him  from 
his  favourite  study. 

Being  looked  upon  with  contempt  by  his  relations,  Tycho 
in  1566  left  Denmark  for  Germany,  settling  at  Wittenberg 
in  April  and  at  Rostock  in  September.  At  Rostock  two 
events  took  place  of  great  interest.  In  the  earlier  part  of 
his  life  Tycho  was  a  firm  believer  in  astrology,  and  he 
declared  that  the  eclipse  of  1 566  foretold  the  death  of  the 
Sultan  of  Turkey.  Some  time  later  the  news  arrived  that 
the  Sultan  was  dead,  but  that  he  had  died  before  the 
eclipse.  It  is  satisfactory  to  know  that  Tycho  gave  up  his 
belief  in  astrology  at  a  later  period  of  his  career.  He  had 
a  violent  temper,  and  in  the  end  of  1566  quarrelled  with 
another  Dane  living  at  Rostock  as  to  which  was  the  better 
mathematician,  the  result  being  that  a  duel  was  fought  in 
which  Tycho  was  seriously  wounded. 

Tycho  Brahe  had  come  to  the  conclusion  that  the  true 
arrangement  of  the  planetary  system  could  not  be  ascertained 
until  the  planets  and  stars  had  been  carefully  observed  and 

279 


THE   EARLY   ASTRONOMERS 

their  positions  noted,  instead  of  relying  on  the  primitive 
and  imperfect  observations  of  the  Greeks  and  Arabs.  After 
leaving  Rostock  he  went  to  Augsburg  and  erected  in  that 
town  for  the  brother  of  the  Burgomaster  a  large  quadrant 
for  noting  the  positions  of  the  stars.  In  those  days  the 
telescope  was  unknown,  and  quadrants  and  sextants  were 
the  principal  instruments  of  astronomers.  In  1570Tycho 
left  Augsburg  for  Denmark.  About  this  time  Tycho's 
time  seems  to  have  been  occupied  with  chemistry,  and  one 
of  his  uncles  permitted  him  to  use  an  outhouse  as  a  labora- 
tory. Tycho  pursued  the  study  of  chemistry  until  1572, 
when  a  great  astronomical  event  finally  directed  his  atten- 
tion to  the  stars. 

On  November  11, 1572,  when  Tycho  was  returning  from 
his  laboratory,  he  observed  a  brilliant  new  star  in  the 
constellation  Cassiopeia.  At  first  it  rivalled  Venus  in 
brilliancy,  and  Tycho's  observations  showed  that  it  had  no 
parallax,  and  was  therefore  among  the  stars  and  did  not 
belong  to  the  planetary  system.  The  light  of  the  star 
now  rapidly  faded,  but  Tycho  made  many  important  obser- 
vations on  it.  He  published  a  book  on  the  star  named 
"  De  Nova  Stella,""  in  which  he  gave  a  detailed  description 
of  all  the  observations  which  he  had  made.  The  publica- 
tion of  this  work  greatly  annoyed  Tycho  Brahe^s  proud 
relations,  who  considered  it  undignified  for  a  nobleman  to 
write  a  book.  In  1574  Tycho  lectured  on  the  stars  in 
Copenhagen,  but  he  had  already  made  up  his  mind  to  leave 
Denmark  and  settle  in  Germany.  King  Frederick  II.  of 
Denmark  saw  that  honour  would  be  conferred  upon  his 
country  if  he  could  persuade  Tycho  to  remain  in  Denmark. 
In  1576,  therefore,  the  King  granted  to  Tycho  a  pension 
and  the  use  of  the  island  of  Hven,  near  Copenhagen,  on 
which  he  might  build  an  Observatory  to  carry  on  his  studies. 

280 


THE  EARLY  ASTRONOMERS 

Tycho  accepted  the  offer,  and  the  Observatory  was  entirely 
completed  by  1 580.  It  was  called  " Uraniaborg,"  or  "The 
City  of  the  Heavens,"  and  it  was  there  that  Tycho  accom- 
plished that  work  which  has  given  him  a  place  among  the 
greatest  astronomers  who  ever  lived.  He  made  observa- 
tions on  the  planets  of  the  utmost  importance,  and  he 
formed  a  star  catalogue.  When  Tycho  went  to  observe 
the  stars  he  put  on  robes  of  state,  as  it  was  his  belief  that 
he  could  not  show  enough  reverence  when  entering  the 
presence  of  the  great  orbs  of  heaven. 

In  1577  Tycho  dealt  a  severe  blow  at  the  authority 
of  Aristotle  by  upsetting  the  ancient  views  of  comets. 
Aristotle  had  declared  that  comets  were  atmospheric  and 
much  nearer  than  the  Moon,  but  Tycho  showed  that  they 
were  situated  among  the  planets.  In  1588  he  published 
a  book  on  the  comet  of  1577,  and  in  this  he  gave  to  the 
world  the  "Tychonic  System."  Tycho  Brahe  was  opposed 
to  the  view  of  Copernicus,  though  he  had  a  high  opinion  of 
that  great  astronomer.  He  likewise  opposed  the  Ptolemaic 
system,  and  was  led  to  found  the  Tychonic  system,  a  com- 
bination of  the  Ptolemaic  and  Copernican  theories,  in 
which  the  planets  were  believed  to  revolve  round  the  Sun, 
which  along  with  the  Moon  and  stars  revolved  round  the 
Earth.  This  error  was,  however,  of  little  importance,  as 
it  was  in  observational  astronomy  that  the  great  work  of 
Tycho  was  accomplished. 

Tycho  remained  at  Hven  for  twenty  years.  In  1588 
King  Frederick  died  and  was  succeeded  by  his  son,  King 
Christian  IV.,  then  only  eleven  years  of  age.  In  1597  he 
took  the  power  into  his  own  hands,  and  several  serious 
charges  were  brought  against  Tycho.  He  had  been  given 
a  cathedral,  which  he  had  allowed  to  fall  into  disrepair. 
He  had  quarrelled  with  one  of  the  people  of  Hven,  and  the 

281 


THE   EARLY  ASTRONOMERS 

high  noblemen  were  jealous  of  his  pension.  Tycho  had  a 
quick  temper,  but  this  does  not  at  all  justify  King  Christian 
in  stopping  Tycho^s  pension,  and  forbidding  him  to  carry 
on  his  observations  at  Copenhagen.  In  June  1 597  Tycho 
and  his  family  left  Denmark  for  ever  and  settled  in  Ger- 
many. The  great  astronomer  moved  restlessly  from  place 
to  place.  He  wrote  from  Rostock  a  humble  and  kindly 
letter  to  the  King,  asking  him  to  restore  his  pension.  But 
Christian  refused,  and  after  two  years  of  wandering  over 
Germany,  Tycho  settled  at  Prague,  in  Bohemia,  in  1599. 
He  was  honoured  by  the  Emperor  Rudolph  of  Bohemia 
by  his  appointment  as  Imperial  Mathematician,  and  in 
1600  Kepler  became  his  assistant. 

But  though  only  fifty-four  years  old  the  anxiety,  and 
exile  from  Denmark,  proved  too  much  for  Tycho,  and  after 
a  short  illness  he  died  at  Prague  on  October  24,  1601. 
For  some  time  before  his  death  he  was  heard  to  exclaim, 
"  Ne  frustra  vixisse  videar  !  " — "  Oh  that  I  may  not  be 
found  to  have  lived  in  vain  !  "  He  asked  Kepler  to  use  the 
observations  made  by  him  and  to  publish  them  as  the 
"  Rudolphine  Tables."  Tycho  was  buried  in  Prague,  where 
a  great  statue  was  erected  to  his  memory.  Had  it  not 
been  for  Tycho,  the  truth  of  the  Copernican  theory,  which 
he  opposed,  would  not  have  been  proved  for  many  years 
after.  To  Tycho  Brahe  we  owe  the  foundation  of  accurate 
observation  which  has  made  astronomy  the  most  exact, 
the  most  wonderful  of  all  the  sciences. 


282 


CHAPTER   XXX 

THE   ROMANCE   OF   DISCOVERY: 
GALILEO   AND   KEPLER 

WHILE  Tycho  Brahe  had  rejected  the  Copernican 
system  in  favour  of  an  idea  of  his  own,  there 
were  living  two  men  who  spread  the  new  theory 
in  Italy  and  Germany.  These  men  were  Giordano  Bruno 
and  Michael  Mastlin.  Bruno  spread  the  new  theory  in 
Italy,  and  also  in  England,  in  a  more  daring  manner  than 
Mastlin  did  in  Germany,  and  for  refusing  to  abjure  his 
belief  he  was  burned  alive  as  a  heretic  at  Rome  in  1600. 
Mastlin  was  the  tutor  of  Kepler,  and  informed  him  of  the 
truth  of  the  system  of  Copernicus.  As  yet,  however, 
nobody  had  proved  the  truth  of  the  theory,  and  when  it 
had  been  rejected  by  such  a  great  man  as  Tycho  Brahe, 
it  seemed  as  if  it  must  still  remain  a  theory.  It  was  here 
that  there  came  into  fame  the  great  Italian  astronomer, 
who  proved  that  the  Copernican  theoiy  was  true,  and  who 
suffered  the  most  cruel  persecution  at  the  hands  of  the 
Church  of  Rome. 

Galileo  de'  Galilei  was  born  at  Pisa  in  1564.  He  was 
the  eldest  son  of  Vincenzo  de  Bonajuti  de1  Galilei,  an 
Italian  nobleman  residing  at  Pisa.  At  first  his  father 
intended  him  to  be  a  cloth  merchant.  He  was  sent  to 
a  school  in  Vallombrosa,  and  made  such  progress  in  his 
studies  that  his  father  decided  that  he  should  adopt  the 
profession  of  medicine.  When  he  was  seventeen  years 


ROMANCE  OF  DISCOVERY:  GALILEO 

of  age  Galileo  entered  the  University  of  Pisa.  In  a 
short  time  he  learned  mathematics,  which  he  studied 
with  great  perseverance,  much  to  the  displeasure  of  his 
father. 

Galileo  had  not  been  long  at  the  University  when  he 
perceived  that  Aristotle  was  by  no  means  an  infallible 
guide  in  scientific  affairs,  and  he  was  not  afraid  to  ridicule 
the  Aristotelian  authority,  much  to  the  annoyance  of  the 
professors  at  Pisa.  He  also  devoted  himself  to  painting 
and  music,  and  for  some  time  intended  to  become  an  artist. 
When  he  was  twenty-one  years  of  age  Galileo  left  the 
University,  and  four  years  later  he  was  appointed  Professor 
of  Mathematics  at  Pisa.  Here  he  made  his  first  great 
attack  on  the  Aristotelians.  Aristotle  had  declared  that 
if  two  bodies  were  dropped  to  the  ground  from  the  same 
height,  the  heavier  would  reach  the  ground  before  the 
lighter.  Galileo  said  that  both  would  reach  the  ground 
simultaneously.  To  prove  that  he  was  correct,  Galileo,  in 
presence  of  a  large  number  of  people,  dropped  two  bodies 
of  unequal  weight  from  the  top  of  the  Leaning  Tower  of 
Pisa.  Both  reached  the  ground  at  the  same  time.  This 
was  a  triumph  for  Galileo,  but  instead  of  admitting  that 
they  had  been  wrong,  the  Aristotelians  made  his  professor- 
ship at  Pisa  so  unpleasant  that  he  resigned.  In  1592 
he  was  appointed  Professor  of  Mathematics  at  Padua. 
Here  he  lectured  on  scientific  subjects  with  great  popular 
success.  In  1602  he  invented  the  thermometer. 

In  a  letter  to  Kepler  in  1597,  Galileo  remarked  that  he 
had  adopted  the  Copernican  system  many  years  before.  At 
first  he  had  laughed  at  the  new  idea,  but  he  found  that, 
while  many  of  the  followers  of  Ptolemy  had  become 
Copernicans,  no  follower  of  Copernicus  ever  adopted  the 
old  system.  Galileo,  however,  was  forced  to  teach  the 

284 


ROMANCE  OF  DISCOVERY:  GALILEO 

Ptolemaic  system  at  the  University,  keeping  his  views  to 
himself. 

But  the  greatest  of  Galileo's  discoveries  had  yet  to 
come.  Hearing  that  Lippershey,  a  Dutch  optician  of 
Middelburg,  had  made  an  instrument  by  which  "  a  man  at 
a  distance  of  two  miles  could  be  clearly  seen,"  Galileo  at 
once  set  about  constructing  an  "  optic  tube,"  as  the  tele- 
scope was  then  called,  and  when  he  had  made  one  there 
was  quite  a  rush  to  see  it.  In  1609  he  presented  a  little 
tube  to  the  Senate  at  Venice.  He  then  made  another  and 
more  powerful  telescope,  the  style  of  which  is  now  known 
as  the  Galilean  refractor.  He  was  amazed  to  find  that  he 
could  see  ten  times  as  many  stars  through  the  telescope 
as  he  could  see  with  the  naked  eye.  He  examined  the 
Pleiades,  Orion,  the  cluster  Prsesepe,  and  other  star 
clusters.  The  Milky  Way  was  now  resolved  into  stars. 

In  January  1610  Galileo  directed  his  telescope  to 
Jupiter.  He  noted  three  stars  near  the  planet.  Next 
night,  to  his  amazement,  he  found  that  the  three  stars  had 
moved  as  well  as  Jupiter.  Some  nights  later  a  fourth 
was  discovered,  and  Galileo  concluded  from  their  changing 
positions  that  they  revolved  round  Jupiter  as  the  Moon 
revolves  round  the  Earth,  and  the  planets  round  the 
Sun.  This  confirmed  the  truth  of  the  Copernican  theory. 
Several  people,  as  already  mentioned  in  a  previous  chapter, 
refused  to  look  into  the  telescope  in  case  they  might  see 
the  satellites  and  be  convinced. 

Galileo  discovered  some  time  later  that  Venus  exhibits 
phases  similar  to  the  Moon.  Copernicus  had  said  that 
Venus  would  show  phases  if  his  theory  was  correct. 
Once  again  Galileo  confirmed  the  truth  of  the  Copernican 
system.  He  also  examined  the  Moon,  and  discovered  that 
its  surface  was  covered  with  mountains  and  craters;  he 

285 


ROMANCE  OF  DISCOVERY:  GALILEO 

found  that  the  Sun  had  black  spots  on  its  surface ;  that 
Mars  showed  phases,  greatly  to  the  disgust  of  the  Aristo- 
telians. Galileo  next  discovered  that  the  planet  Saturn  was 
elliptical  in  shape,  but  he  could  not  explain  the  cause.  It  was 
not  explained  until  Huyghens  took  up  the  subject  in  1656. 

Galileo  left  Padua  in  1610,  and  went  to  Florence  with 
the  title  of  Mathematician  and  Philosopher  to  the  Grand 
Duke  of  Tuscany.  In  leaving  Padua  he  made  a  great 
blunder  in  transferring  himself  from  the  free  Republic  of 
Venice  to  Tuscany,  where  the  Church  of  Rome  was  all- 
powerful.  At  length  Galileo^s  ideas  about  the  Universe, 
now  widely  known,  were  pronounced  to  be  opposed  to  the 
Bible.  In  1615  he  went  to  Rome  and  continued  to  teach 
the  Copernican  theory.  For  this  he  was  summoned 
before  the  Inquisition,  and  the  Copernican  system  was 
condemned.  Pope  Paul  V.  warned  Galileo  not  to  teach 
the  new  system  as  if  it  were  true. 

After  Paul  V.  was  dead,  in  1623  Cardinal  Barberini 
was  elected  Pope  as  Urban  VIII.  The  Pope  had  been, 
while  still  a  cardinal,  a  great  friend  and  admirer  of  Galileo, 
and  the  astronomer  therefore  considered  that  he  was  now 
at  liberty  to  teach  the  Copernican  theory.  He  prepared 
to  write  his  work,  "  The  Dialogue  of  the  Two  Principal 
Systems  of  the  World,  the  Ptolemaic  and  the  Copernican." 
It  was  written  in  the  form  of  conversations  between  three 
men.  Galileo  was  very  careful,  and  by  writing  it  in  the 
form  of  conversation,  which  did  not  indicate  the  views  of 
the  author,  he  obtained  permission  from  the  Pope  and  the 
Inquisition  to  have  his  work  published.  The  book  was 
given  to  the  world  in  June  1632.  Presently,  however, 
the  Church  of  Rome  regretted  having  allowed  the  publi- 
cation. One  of  the  characters  in  the  dialogue  was  named 
"  Simplicius,"  and  it  was  he  who  upheld  the  Ptolemaic 

286 


ROMANCE  OF  DISCOVERY:  GALILEO 

system.  Some  ignorant  priests  represented  to  the  Pope  that 
"  Simplicius  "  was  meant  to  represent  himself  and  hold  him 
up  to  ridicule.  Orders  were  then  given  for  the  seizure  of 
every  copy  of  the  book,  which  was  condemned  as  heretical. 

The  Pope  ordered  Galileo  to  appear  before  the  Inquisi- 
tion at  Rome.  Being  sixty-nine  years  of  age,  he  begged  to 
be  excused  from  the  journey.  But  Urban,  acting  in  much 
the  same  hard-hearted  manner  as  the  King  of  Denmark  had 
acted  towards  Tycho  Brahe,  was  enraged  and  said  that 
the  command  must  not  be  disobeyed.  In  February  1633 
Galileo  arrived  in  Rome,  and  four  months  later  was  tried 
before  the  Inquisition  for  teaching  the  Copernican  system. 
On  June  22  he  was  compelled  to  kneel  before  the  cardinals 
of  the  Roman  Church,  and,  with  threats  of  death,  was 
ordered  to  declare  that  he  would  in  future  "  detest  the 
false  opinion  that  the  Sun  was  the  centre  of  the  Universe 
and  that  the  Earth  moved."  Rising  from  his  knees,  tradi- 
tion says,  he  whispered  to  one  standing  near  him — "  E  pur 
se  muove  !  "— "  For  all  this,  it  does  move  ! " 

Galileo  was  sentenced  to  be  imprisoned  as  long  as  Pope 
Urban  desired.  His  health,  however,  suffered  from  the 
intense  heat  at  Rome,  and  he  was  allowed  to  return  to  his 
house  at  Arcetri,near  Florence,  in  which  he  was  commanded 
to  remain  in  everlasting  solitude.  At  last  came  the  tragedy 
at  the  end  of  his  life.  His  sight  began  to  fail,  and  in  the 
end  of  1 637  he  became  totally  blind.  On  January  2, 1 638, 
he  wrote  thus  to  a  friend :  "  Alas,  your  dear  friend  and 
servant  Galileo  has  been  for  the  last  month  perfectly  blind, 
so  that  this  Heaven,  this  Earth,  this  Universe,  which  with 
wonderful  observations  I  had  enlarged  a  hundred,  a 
thousand  times  beyond  the  belief  of  bygone  ages,  hence- 
forth for  me  is  shrunk  into  the  narrow  space  which  I  myself 
fill  in  it.  So  it  pleases  God  ;  it  shall  therefore  please  me 

287 


ROMANCE  OF  DISCOVERY:  KEPLER 

also.11  Galileo  died  at  Arcetri  on  January  8,  1642,  aged 
seventy-seven,  having  been  blind  for  four  years.  Even 
after  he  was  dead  the  Pope  would  not  allow  a  monument 
to  be  erected  to  his  memory.  Still,  despite  the  foolish 
attempt  to  crush  the  Copernican  system,  Galileo,  though 
he  died  in  misery,  was  in  the  end  triumphant. 

While  Galileo  was  confirming  the  Copernican  theory  by 
observation,  another  great  man  was  confirming  it  by  mathe- 
matics. By  means  of  difficult  calculations  he  made  dis- 
coveries as  brilliant  as  Galileo  made  with  the  telescope, 
and  his  calculations,  which  were  based  on  Tycho  Brahe's 
observations  at  Uraniaborg,  finally  led  to  Newton's  dis- 
covery of  universal  gravitation.  The  name  of  this  man 
was  Johann  Kepler.  He  was  born  at  Weil  der  Stadt,  in 
the  duchy  of  Wiirtemberg,  in  Germany,  in  1571,  and  was 
thus  the  first  of  those  great  German  astronomers  to  whom 
science  has  owed  so  much.  Kepler  was  the  son  of  a  soldier, 
and  his  grandfather  was  the  Burgomaster  of  Weil  der 
Stadt.  Kepler,  who  was  always  in  very  poor  circumstances, 
was  educated  at  the  school  at  Maulbraun,  which  was  pre- 
paratory to  the  University  of  Tubingen.  At  length,  when 
he  was  seventeen  years  of  age,  he  entered  the  University  of 
Tubingen,  and  learned  from  Mastlin,  the  Professor  of  Mathe- 
matics there,  that  the  Copernican  theory  was  the  true  one. 
When  Kepler  left  the  University  he  was  without  means, 
and  had  no  prospect  of  employment.  Shortly  afterwards, 
however,  the  Professorship  of  Astronomy  at  Gratz  fell 
vacant  through  the  death  of  the  Professor,  and  Kepler,  who 
as  yet  had  no  special  inclination  for  astronomy,  was  offered  it 
and  urged  by  his  friends  to  accept  it,  which  he  did  with  con- 
siderable reluctance.  He  was  then  twenty-three  years  of  age. 

It  was  while  he  was  at  Gratz  that  Kepler  hit  upon  a 
theory  which,  though  long  since  discarded,  was  very  ingenious. 

288 


ROMANCE  OF  DISCOVERY:   KEPLER 

He  considered  that  the  "  five  regular  solid  figures  "  known 
to  mathematicians  corresponded  with  the  five  planets, 
Mercury,  Venus,  Mars,  Jupiter,  and  Saturn.  The  idea  was 
a  daring  one,  but  is  now  absolutely  useless.  All  the  same 
it  made  Kepler  prominent  in  the  world  of  science.  He 
wrote  a  book  advocating  it,  and  by  means  of  this  book  he 
became  known  to  Tycho  Brahe  and  Galileo.  As  the  in- 
habitants of  Gratz  were  chiefly  Roman  Catholics,  all  the 
Protestant  Professors  were  expelled  in  1599,  Kepler  among 
them.  But  he  had  now  become  a  famous  man  of  science, 
and  he  was  restored  to  his  position.  However,  he  had  no 
pupils,  and  he  was  glad  in  1600  to  accept  the  post  of 
assistant  to  Tycho  Brahe  near  Prague. 

When  Tycho  Brahe  was  dying  in  1601  he  requested 
Kepler  to  use  his  observations,  which  had  been  collected  at 
Uraniaborg  from  1577  to  1597,  believing  that  by  means 
of  these  observations  the  true  system  of  the  Universe  would 
at  last  be  revealed.  After  Tycho's  death  Kepler  was 
appointed  to  succeed  him  as  "  Imperial  Mathematician  "  to 
the  Emperor  Rudolph.  He  was  promised  a  handsome  salary 
in  his  new  post,  but  it  was  never  paid.  Tycho  expressed 
the  wish  that  the  observations  might  be  continued  after 
his  death,  but  this  wish  was  not  to  be  fulfilled.  Kepler, 
faithful  to  the  last  wishes  of  the  Danish  astronomer,  com- 
menced to  observe  Mars  with  the  great  telescopes  which 
Tycho  had  brought  from  Uraniaborg.  In  1602,  however, 
Tycho's  son-in-law  Tengnagel,  who  pretended  to  be  inter- 
ested in  astronomy  and  was  jealous  of  Kepler,  deprived  him 
of  the  instruments,  and  promised  the  Emperor  Rudolph  that 
the  planetary  tables  would  be  finished  within  four  years. 
Kepler  never  saw  the  instruments  again,  as  they  were  stored 
away  in  an  old  vault,  and  they  were  probably  destroyed  in 
the  Bohemian  rebellion  of  1619.  As  to  the  observations 

289  T 


ROMANCE  OF  DISCOVERY:   KEPLER 

of  Tycho,  Kepler  at  last  got  access  to  them,  and  Tengnagel 
soon  abandoned  the  idea  of  working  at  the  Rudolphine 
tables,  which  now  occupied  the  attention  of  Kepler. 

As  has  been  already  mentioned,  Kepler's  promised  salary 
was  never  paid,  and  for  years  he  was,  as  he  himself  remarked, 
"begging  his  bread  from  the  Emperor.'"  Owing  to  his 
poverty  he  was  unable  to  publish  the  Rudolphine  tables 
for  about  twenty  years.  Some  time  after  the  death  of 
Tycho,  Kepler  published  a  book  on  comets.  In  1609  he 
published  "  Commentaries  on  the  Motions  of  Mars,11  the 
work  which  contained  the  first  of  the  three  laws  of  planetary 
motion,  which  showed  that  the  planets  revolved  round  the 
Sun  in  elliptical  orbits.  Kepler  could  not  reconcile  the 
observations  of  Tycho  with  the  theory  of  circular  orbits. 
There  was  not  a  very  large  difference,  and  many  men  would 
have  accounted  for  the  difference  by  the  supposition  that 
Tycho  had  made  a  mistake,  and  would  thus  have  lost  the 
chance  of  making  a  great  discovery.  But  Kepler  knew 
Tycho  Brahe,  and  he  was  certain  that  the  great  astronomer 
could  not  have  made  so  large  an  error.  Kepler's  second 
law  was  published  in  a  few  years  after  the  first.  The 
irregularities  in  the  motions  of  the  planets  were  now 
accounted  for,  and  the  great  laws  of  Kepler  removed  the 
difficulties  which  stood  in  the  way  of  the  acceptance  of  the 
Copernican  system,  and  confirmed  it  as  conclusively  as  did 
the  telescopic  observations  of  Galileo.  The  observations 
of  Tycho  Brahe  confirmed  the  system  of  Copernicus,  which 
he  himself  had  rejected. 

Kepler  was  still  in  extremely  poor  circumstances,  and 

accordingly  he    asked   the    Emperor   to   pay  his   salary. 

Rudolph  ordered  it  to  be  paid,  but  the  Bohemian  exchequer 

was  empty.     In  1610,  the  year  of  Galileo's  great  telescopic 

^'discoveries,  Kepler  suffered  almost  every  sorrow  imaginable. 

290 


ROMANCE  OF  DISCOVERY:   KEPLER 

He  was  in  great  poverty ;  the  Austrian  troops  occupied 
Prague,  his  wife  died,  and  his  favourite  son  also  died.     He 
went  to  Austria  to  secure  a  professorship  at  Linz,  but 
Rudolph  would  not  allow  him  to  leave  Prague,  and  promised 
to  pay  his  salary,  but  again  failed  to  keep  his  promise.    At 
this  time  Kepler  was  in  such  extreme  poverty  that  he  was 
compelled  to  write  what  he  called  "a  vile  prophesying 
almanac,"  filled  with  astrology,  in  which  he  did  not  believe. 
It  has  been  pointed  out  as  remarkable  that  "the  world 
would  not  give  him  bread  for  his  astronomical  discoveries, 
but  it  would  give  him  money  for  what  he  knew  to  be  lies." 
Rudolph  died  in  1612,  and  the  new  Emperor  Mathias,  his 
brother,  allowed  the  astronomer  to  accept  the  professorship 
at  Linz,  and  asked  him  to  also  retain  the  position  at  Prague. 
During  all  his  misfortunes  Kepler  exhibited  a  beautiful 
nature.     In  January  1610  the  satellites  of  Jupiter  were 
discovered  by  Galileo.      Kepler  was  the  only  man  who 
accepted  the  discovery  without  hesitation,  even  though  it 
ran  counter  to  his  ideas  of  the  "  five  regular  solids."     He 
welcomed  the  news  of  his  friend's  success.     A  follower  of 
Kepler  attacked  Galileo,  accusing  him  of  having  plagiarised 
some  of  the  former's  discoveries,  for  which  Kepler  compelled 
the  man  to  apologise  to  the  Italian  astronomer.     Another 
instance  of  his  fine  nature  can  be  given.   "  One  of  his  rejected 
theories,"  writes  one  of  his  biographers,  "  assumed  a  new 
planet  between  Mars  and  Jupiter.     Kepler  was  afraid  that 
this  might  be  mistaken  by  a  careless  reader  to  be  an  anticipa- 
tion of  Galileo's  discovery  of  the  satellites  of  Jupiter ;  and 
so  in  a  subsequent  edition  of  his  work  ('  The  Five  Regular 
Solids')  published  in  1621,  he  adds  a  note  referring  to  his 
supposed  planet :    '  Not  circulating  round  Jupiter  like  the 
Medicean l  stars.     Be  not  deceived.     I  never  had  them  in 
my  thoughts.'"   Before  leaving  this  subject,  it  may  be  noted 
1  Another  name  for  the  satellites  of  Jupiter. 

291 


ROMANCE  OF  DISCOVERY;   KEPLER 

that  Kepler's  prediction  of  a  planet  between  Mars  and 
Jupiter  was,  as  we  have  seen,  confirmed  by  the  discovery  of 
the  early  asteroids  by  Piazzi  and  Olbers  a  hundred  years  ago. 

Kepler  was  soon  expelled  from  Linz  on  account  of  his 
Protestantism.  He  refused  in  1617  to  accept  a  professor- 
ship at  Bologna  with  a  large  salary.  In  1619  he  published 
his  third  law  in  a  work  entitled  "  The  Harmonies  of  the 
World,"  dedicated  to  King  James  VI.  of  Scotland.  The 
discovery  of  this  law  was  the  aim  of  his  life.  In  1622 
he  wrote  the  "  Epitome  of  the  Copernican  Astronomy,11 
defending  the  Copernican  system.  The  book  was  at  once 
prohibited  by  the  Church  of  Rome.  At  last  in  1621,  the 
Rudolphine  tables,  the  result  of  the  labours  of  Tycho  Brahe, 
were  published,  and  in  recognition  of  this  work,  and  of  his 
services  to  astronomy,  Kepler  received  a  gold  chain  from  the 
Grand  Duke  of  Tuscany.  In  1620  a  proposal  was  made 
to  Kepler  that  he  should  leave  Germany  and  go  to  England. 
But  he  declined  to  leave  his  native  country. 

When  Kepler  was  fifty-seven  years  of  age,  he  received  an 
offer  to  live  under  the  protection  of  the  Duke  of  Freidland. 
A  professorship  at  Rostock  was  also  given  to  the  great 
astronomer,  and  his  future  career  seemed  hopeful.  Before 
leaving  Bohemia,  however,  he  made  a  journey  to  Ratisbon  to 
procure  the  salary  which  had  never  been  paid  to  him.  But 
anxiety  about  the  payment  of  his  money  proved  too  much 
for  him.  His  health,  always  delicate,  gave  way,  and  while  at 
Ratisbon  he  was  seized  with  illness  and  died  in  1630.  He 
was  buried  in  St.  Peter's  Church  in  Ratisbon,  where  a  hun- 
dred years  ago  a  great  statue  was  erected  to  his  memory. 

The  last  of  the  great  astronomers  before  Newton  was 
Huyghens,  the  Dutch  scientist.  Huyghens  was  born  at  the 
Hague  in  1 629.  He  was  the  second  son  of  the  Dutch  poet, 
Constantine  Huyghens,  counsellor  to  the  Prince  of  Orange. 
When  he  was  thirteen  years  of  age,  Huyghens  began  to  take 

292 


ROMANCE  OF  DISCOVERY:   KEPLER 

much  interest  in  mathematical  studies,  and  examined  every 
piece  of  machinery  he  could  lay  hold  of.  He  was  educated 
at  the  University  of  Leyden,  and  was,  like  Tycho  Brahe, 
intended  to  study  law,  for  which  he  was  sent  to  Breda. 
But  the  bent  of  his  mind  was  towards  science,  and  when 
he  was  twenty-four  years  of  age  he  wrote  some  treatises 
on  geometry,  studying  that  subject  until  1651,  when  he 
devoted  himself  to  observational  astronomy. 

Since  the  death  of  Galileo,  the  founder  of  telescopic 
observation,  there  had  been  little  improvement  in  the 
making  of  telescopes,  and  no  further  discoveries  had  been 
made  in  the  celestial  regions.  The  mystery  of  Saturn,  which 
puzzled  Galileo,  remained  a  mystery ;  nothing  was  known 
regarding  nebulae,  while,  with  the  exception  of  Galileo's 
discoveries  of  the  Martian  phases  and  a  few  observations  by 
Fontana  at  Naples  in  1636  and  1638,  the  study  of  the  planet 
Mars  had  not  yet  been  begun  ;  in  fact,  until  Huyghens 
arrived  upon  the  scene,  telescopic  observation  remained  at 
a  stand  still.  In  1655  Huyghens,  with  the  help  of  his 
brother,  set  about  telescope-making.  By  a  new  method 
he  ground  and  polished  lenses  which  were  much  more  power- 
ful and  much  more  perfect  then  those  used  by  Galileo. 
Huyghens  then  commenced  to  observe  the  planet  Saturn 
in  order  to  solve  the  mystery  of  its  elliptical  appearance. 
As  mentioned  in  a  previous  chapter,  the  famous  ring  of 
Saturn  was  detected  by  Huyghens.  He  was  also  the  first 
to  study  nebulae.  On  June  16, 1659,  he  presented  the  first 
"  pendulum  clock  "  to  the  States-General  of  Holland,  the 
invention  being  the  result  of  accurate  astronomical  observa- 
tions. Huyghens  in  1660  visited  England,  where  he  solved 
some  problems  in  mathematics.  He  left  Holland  in  1665, 
and  settled  in  Paris  at  the  invitation  of  Louis  XIV.  In 
France  he  devoted  himself  to  other  researches  besides 
astronomy  and  mathematics.  Like  his  illustrious  con- 


ROMANCE  OF  DISCOVERY:    KEPLER 

temporary  Newton,  he  speculated  in  chemistry,  and  dis- 
covered the  true  nature  of  light,  which  perhaps  forms  the 
boundary  line  between  astronomy  and  chemistry.  He  found 
that  light  travels  through  space  in  the  form  of  waves,  a  view 
which  did  not  command  universal  acceptance  until  about  a 
hundred  years  ago,  when  it  was  revived  and  established. 

Huyghens  remained  in  Paris  until  1681,  when  the  per- 
secution of  the  Protestants  compelled  him  to  return  to 
Holland.  Here  he  continued  his  astronomical  observa- 
tions. He  constructed  telescopes  of  enormous  length 
known  as  "aerial  telescopes,"  and  three  of  his  object- 
glasses  are  still  in  the  possession  of  the  Royal  Society. 
He  invented  an  almost  perfect  eyepiece,  known  as  the 
"Huyghenian  eyepiece,"  which  is  still  extensively  used. 
It  is  also  interesting  to  know  that  Huyghens  was  one  of 
the  strongest  supporters  of  the  theory  of  life  on  other 
worlds.  In  his  work,  the  "  Cosmotheoros  "  (published  at 
the  Hague  in  1698,  shortly  after  his  death),  he  speculated 
regarding  the  possible  inhabitants  of  the  planets,  and 
brought  forward  arguments  in  favour  of  the  plurality  of 
worlds.  Unfortunately  Huyghens  did  not  accept  Newton's 
view  that  gravitation  was  universal,  although  he  admitted 
that  it  regulated  the  movements  of  the  planets.  It  was 
with  considerable  difficulty  that  he  could  accept  the  views 
of  others,  but  it  has  been  pointed  out  that  this  was  not 
due  to  unwillingness  to  acknowledge  the  merits  of  his 
contemporaries.  He  was  unable  to  depart  from  his  own 
methods.  It  may  be  noted  that  Newton  rejected  two  of 
Huyghen's  theories,  one  of  these  being  the  nature  of 
light.  Huyghens  died  at  the  Hague  in  1695,  at  the  age 
of  sixty-six.  His  career  closed  an  epoch  in  astronomy  which 
prepared  the  way  for  the  work  of  the  mightiest  intellect 
which  has  ever  applied  itself  to  the  problems  of  the  heavens. 


CHAPTER   XXXI 
NEWTON   AND   HIS   SUCCESSORS 

THE    work    of  Kepler   prepared    the   way    for   the 
greatest  discovery  ever   made    in   the  history  of 
astronomy.     In   the   first    chapter  reference   was 
briefly  made  to  the  marvellous  fact  of  gravitation.     But 
gravitation  is  never  thought  of  or  spoken  of  apart  from 
its  discoverer.    It  is  "  the  Newtonian  Law."    It  is  never  dis- 
sociated from  the  mighty  intellect  which  first  revealed  it. 
Kepler  had  detected  the  laws  of  the  planetary  motions, 
but  he  was  unable  to  show  the  cause  of  these  motions. 
The  hour  had  come  for  the  discovery  of  the  fundamental 
law  of  the  Universe,  and  with  the  hour  came  the  man. 
Isaac  Newton,  the  illustrious  astronomer,  was  the  son  of  a 
Lincolnshire  farmer.     Born  at  Woolsthorpe,  near  Grant- 
ham  in  1642,  he  was  sent  at  the  age  of  twelve  to  a  school 
at  Grantham.     At  first  he  was  very  idle  in  his  studies, 
but  it  was  not  long  before  he  began  to  take  an  interest 
in  constructing  mechanical  models  and  sundials.     One  of 
these  dials  still  remains  at  Woolsthorpe.     When  he  was 
fourteen  years  of  age,  Newton  was  removed  from  the  school 
by  his  mother,  who  desired  him  to   become   a  farmer, 
hoping  that  he  would  now  lay  aside  his  books  and  the 
studious  habits  to  which  he  had  become  addicted.     On  one 
occasion  Newton  was  sent  in  company  with  an  old  farm 
servant  to  a  neighbouring  town  to  sell  the  products  of 
the  farm.     The  young  astronomer,  however,  preferred  to 

295 


NEWTON  AND   HIS   SUCCESSORS 

leave  the  disposal  of  the  products  to  his  companion,  and 
interested  himself  in  a  collection  of  old  books  which  he 
had  found  in  a  garret. 

One  of  his  uncles  found  him  one  day  sitting  behind  a 
hedge  reading  a  book  on  abstruse  mathematics  instead  of 
attending  to  the  farm.  It  was  clear  that  he  would  not 
make  a  good  farmer,  and  his  mother,  at  his  uncle's  sug- 
gestion, wisely  resolved  to  send  him  to  the  school  to  pre- 
pare for  the  University.  On  June  5,  1660,  when  he  was 
seventeen  years  of  age,  Newton  entered  the  University  of 
Cambridge,  and  soon  afterwards  finally  turned  to  astro- 
nomy and  mathematics.  In  1664  and  1665  his  excessive 
study  of  mathematics  brought  on  ill  health,  which  was 
intensified  by  sitting  up  at  night  to  observe  a  comet. 
He  made  such  progress  in  his  studies  that  in  1669,  when 
in  his  twenty-seventh  year,  he  was  appointed  Lucasian 
Professor  of  Mathematics  at  Cambridge. 

Among  Newton's  early  studies  were  his  investigations 
on  light.  He  was  much  interested  in  it,  and  was  the  first 
to  disperse  it  in  a  prism.  He  showed  that  white  light 
was  actually  composed  of  the  seven  colours,  red,  yellow, 
orange,  green,  blue,  indigo,  and  violet.  But  he  could 
never  have  foreseen  the  discoveries  made  in  the  nineteenth 
century.  He  formulated  a  theory  of  light  opposed  to  the 
true  view  of  Huyghens,  supposing  light  to  be  caused  by 
the  emission  of  minute  particles  from  the  celestial  bodies. 
He  was  so  great  a  man  in  comparison  with  Huyghens,  that 
his  theory  was  believed  for  over  a  hundred  years. 

Isaac  Newton's  researches  regarding  light  prepared  the 
way  for  the  invention  of  the  reflecting  telescope.  Galileo, 
as  already  mentioned,  was  the  first  to  invent  the  refractor. 
It  was  soon  found  that  as  the  size  of  the  instrument  was 
increased,  the  field  of  view  was  impaired  by  a  defect  known 

296 


NEWTON   AND   HIS   SUCCESSORS 

as  chromatic  aberration.  In  fact,  the  object-glasses,  like 
prisms,  dispersed  the  light  into  its  primary  colours.  To 
counterbalance  this  difficulty,  Huyghens  and  Hevelius 
made  telescopes  of  enormous  focal  length ;  but  this  could 
not  go  on  for  ever,  and  Newton,  in  his  investigations  on 
the  subject,  came  to  the  conclusion  that  it  was  impossible 
to  produce  a  telescope  which  would  be  free  from  chromatic 
aberration.  We  know  that  he  was  wrong,  as  several 
English  opticians  afterwards  succeeded  in  constructing 
telescopes  free  from  this  defect,  and  known  as  achromatic 
refractors. 

Perhaps,  however,  it  was  as  well  for  astronomy  that 
Newton  erred  in  regard  to  the  telescope.  He  determined 
to  make  a  telescope  which  did  not  depend  upon  refraction, 
and  constructed  a  concave  mirror  by  a  combination  of 
copper  and  tin  which  shone  with  the  lustre  of  silver.  He 
then  fixed  it  at  the  bottom  of  a  tube,  and  the  images  of 
the  stars  were  examined  by  means  of  a  magnifying  eye- 
piece. The  little  telescope  was  only  one  inch  in  diameter, 
but  all  the  same  it  distinctly  showed  the  satellites  of 
Jupiter  and  the  phases  of  Venus.  It  is  now  preserved  by 
the  Royal  Society  of  London  in  memory  of  the  great  astro- 
nomer. This  invention  was  an  invaluable  boon  to  science, 
and  gigantic  reflectors  have  since  been  constructed  on 
Newton's  principle  by  Herschel,  Rosse,  and  other  eminent 
astronomers. 

In  1666,  as  previously  mentioned,  he  began  his  investi- 
gations of  the  subject  of  gravitation.  Whether  the  well- 
known  story  of  the  apple  is  true  or  not,  it  is  an  excellent 
illustration  of  Newton's  line  of  reasoning.  The  story  is 
that,  in  1666,  as  Newton  was  sitting  in  his  garden  at 
Woolsthorpe,  the  fall  of  an  apple  led  him  to  ask  if  gravi- 
tation, already  known  to  exist  on  the  Earth,  and  which 

297 


NEWTON   AND   HIS   SUCCESSORS 

caused  the  apple  to  fall,  did  not  also  hold  the  Moon  to 
the  Earth.  The  great  discovery  was  made.  Having  ex- 
tended gravitation  to  the  Moon,  the  great  astronomer  could 
likewise  extend  it  to  the  solar  system.  By  this  method  the 
Laws  of  Kepler  were  shown  to  be  the  natural  outcome  of 
universal  gravitation. 

All  this  may  seem  very  simple,  but  a  great  number  of 
difficulties  lay  before  Newton.  He  could  not  reconcile 
several  facts  regarding  the  Moon  with  the  theory  of  gravi- 
tation, and  he  abandoned  the  subject  until  1684.  At  that 
time  a  discussion  was  proceeding  in  London  between  the 
astronomer  Halley,  the  scientist  Hook,  and  the  architect 
Sir  Christopher  Wren  regarding  the  movement  of  a  planet 
according  to  gravitation.  Hook,  who  was  a  jealous  and 
vain  man,  tried  to  make  people  believe  that  he  had  the 
solution,  but  would  not  give  it  to  the  world  until,  by 
attempting,  people  had  found  out  how  difficult  it  was,  and 
would  thereby  honour  the  discoverer.  Halley,  in  order  to 
get  more  light  on  the  subject,  asked  Newton,  who,  to  his 
surprise,  solved  it  at  once.  Halley  urged  Newton  to  pub- 
lish his  discoveries  regarding  universal  gravitation.  At 
that  time  also,  new  measurements  regarding  the  Moon's 
distance  had  removed  the  difficulties  which  had  hindered 
the  establishment  of  the  law  of  gravitation.  Newton, 
therefore,  published  his  discoveries  in  his  great  work  the 
"  Principia,"  which  was  given  to  the  world  in  1687.  In 
this  work  he  showed  the  tides  also  to  be  the  outcome  of 
gravitation.  In  fact,  he  announced  the  great  law  that 
"  every  particle  of  matter  in  the  Universe  attracts  every 
other  particle."  This  discovery  was  not,  however,  at  once 
accepted.  Huyghens  rejected  it,  though  admitting  that 
gravitation  ruled  the  planetary  motions.  The  clergy  pro- 
nounced it  to  be  impious,  and  it  was  a  long  time  before  it 

298 


NEWTON  AND   HIS   SUCCESSORS 

was  taught  in  the  universities.     Still,  like  all  true  theories, 
it  triumphed. 

It  happened  that  Newton  was  not  a  rich  man,  and  was 
unable  to  pay  for  the  publication  of  the  "  Principia." 
The  Royal  Society  was  also  without  available  funds,  and 
the  result  was  that  Halley  generously  had  the  book  pub- 
lished at  his  own  expense.  Halley  was  Newton's  most 
devoted  friend,  and  their  friendship  continued  without  in- 
terruption. After  the  publication  of  his  book  Newton 
speculated  in  chemistry,  but  all  his  labours  were  lost  by  an 
unfortunate  accident.  One  morning  he  went  to  church 
leaving  a  lighted  candle  among  the  papers  on  his  desk. 
It  is  said  that  his  pet  dog,  "  Diamond,"  upset  the  candle. 
When  the  astronomer  came  home,  he  found  all  his  papers 
destroyed.  He  exclaimed  "  O  Diamond,  Diamond  !  thou 
little  knowest  the  mischief  thou  hast  done  !  "  His  health 
was  impaired  by  the  accident,  and,  though  only  about  fifty 
years  old  at  the  time,  he  made  no  more  great  discoveries. 

In  1687,  Newton  came  prominently  before  the  public. 
In  that  year  when  James  II.  attempted  to  infringe  on  the 
rights  of  the  University  of  Cambridge,  Newton  was  one  of 
the  nine  men  who  defended  the  conduct  of  the  University, 
and  won  the  case.  In  1688  he  represented  the  University 
in  Parliament,  and  for  two  years  retained  his  seat.  At 
length  many  of  his  friends  began  to  think  that  he  should 
get  some  honour  or  appointment.  Mr.  Charles  Montague, 
a  great  friend  of  Newton,  was  appointed  Chancellor  of  the 
Exchequer  in  1694,  and  in  1695  he  offered  the  position  of 
Warden  of  the  Mint  to  the  astronomer,  who  accepted  it, 
his  knowledge  of  physics  being  of  much  use  to  him  in  his 
new  sphere.  In  1697,  the  position  of  Master  of  the  Mint 
fell  vacant,  and  Newton  was  appointed  to  that  office.  He 
soon  found,  however,  that  he  could  not  discharge  his 

299 


NEWTON   AND   HIS  SUCCESSORS 

duties  both  at  the  Mint  and  at  Cambridge,  and  in  1701 
he  resigned  his  professorship,  and  severed  his  connection 
with  the  University. 

In  1703  Newton  was  elected  President  of  the  Royal 
Society,  a  position  which  he  held  until  the  end  of  his  life. 
In  1705  he  was  knighted  by  Queen  Anne  in  recognition 
of  his  great  discoveries.  He  now  resided  in  London,  and 
during  the  remaining  years  of  his  life  he  was  chiefly  occu- 
pied with  his  duties  at  the  Mint  and  at  the  Royal  Society, 
and  his  mathematical  and  theological  studies.  He  was 
deeply  interested  in  theology,  being  of  an  extremely  re- 
ligious temperament.  On  March  20,  1727,  Sir  Isaac 
Newton  died  in  London,  after  a  long  illness,  at  the  age  of 
eighty-four.  A  week  later  he  was  buried  in  Westminster 
Abbey.  A  magnificent  statue  was  afterwards  erected  to 
his  memory  at  Cambridge,  where  he  is  represented  as  hold- 
ing in  his  hand  a  prism.  Another  memorial  to  England's 
greatest  astronomer  was  erected  in  Lincolnshire  in  1858. 
Considering  the  vast  importance  of  his  discoveries,  Sir  Isaac 
Newton  was  in  no  way  elated.  He  was  always  ready  to 
acknowledge  what  he  owed  to  the  great  men  who  preceded 
him.  "  If  I  have  seen  farther  than  other  men,"  he  said, 
"  it  is  because  I  have  stood  on  the  shoulders  of  the  giants." 
His  prevailing  humility  is  well  expressed  by  him  in  his  old 
age,  when  he  compared  himself  to  a  little  child  on  the  sea- 
shore gathering  pebbles.  He  had  picked  one  or  two  from 
the  waves,  but  the  infinite  treasures  remained  undiscovered. 

Newton's  chief  contemporaries,  Flamsteed  and  Halley, 
were  the  first  and  second  holders  of  the  office  of  Astro- 
nomer Royal  of  England.  Both  were  distinguished  men. 
Flamsteed  was  the  elder  of  the  two,  and,  like  Hipparchus 
and  Tycho,  was  essentially  a  practical  astronomer.  His 
Star  Catalogue,  constructed  at  Greenwich,  is  a  standard 

300 


NEWTON  AND   HIS   SUCCESSORS 

work,  and  has  been  for  many  years  a  book  of  reference  to 
astronomers  all  over  the  world.  Flamsteed  died  in  1719, 
after  a  life  of  usefulness  and  activity.  Halley,  who  suc- 
ceeded him,  was  more  of  a  brilliant  genius,  and  less  of  a 
steady  observer  than  Flamsteed.  Born  in  1656,  he  was 
the  son  of  Edmund  Halley,  a  wealthy  soap  boiler  in 
London.  Young  Halley  from  his  earliest  years  showed 
interest  in  mechanical  invention.  He  was  educated  at 
St.  Paul's  School,  in  London,  and  by  the  time  he  left  the 
school  he  had  made  much  progress  in  astronomy  and 
mathematics.  At  the  age  of  seventeen  he  entered  the 
University  of  Oxford.  At  this  time  he  was  deeply 
interested  in  mathematics,  and  solved  some  questions  re- 
garding movement  in  an  ellipse ;  and  at  the  age  of 
nineteen  he  published  a  mathematical  treatise. 

Halley  had  no  intention  of  being  merely  an  astronomer 
on  paper.  He  longed  to  start  the  practical  work  of  ob- 
serving. This  was  an  easy  matter,  for  not  only  was  his 
father  wealthy,  but  he  was  a  wise  man ;  and  was  anxious 
that  his  son  should  take  up  the  subject  in  which  he  was 
most  interested.  He  therefore  gave  him  an  allowance  of 
£200.  The  young  astronomer  desired  to  follow  Tycho 
Brahe's  example  in  determining  the  positions  of  the  stars 
with  great  accuracy.  Finding,  however,  that  Flamsteed  of 
Greenwich  and  Hevelius  of  Dantzig  were  engaged  on  work 
of  the  same  kind,  he  determined  to  visit  the  island  of 
St.  Helena  to  observe  the  southern  stars,  which  until  then 
had  been  neglected. 

Halley  left  Oxford  University  before  taking  his  degree, 
and  set  sail  in  1676  when  in  his  twentieth  year,  in  an 
East  India  Company  ship.  Three  months  later  he  arrived 
at  St.  Helena,  having  with  him  a  sextant  and  a  telescope 
24  feet  in  focal  length.  The  climate  of  the  island,  how- 

301 


NEWTON   AND   HIS   SUCCESSORS 

ever,  proving  unfavourable,  Halley  remained  for  one 
year  only.  All  the  same,  he  accomplished  much  valuable 
work,  which  gained  for  him  the  title  of  "  Our  Southern 
Tycho." 

In  1677  the  astronomer  returned  to  England,  and 
through  the  influence  of  King  Charles  II.  he  was  made  a 
Master  of  Arts  at  Oxford  in  the  following  year.  In  1678 
he  was  elected  a  Fellow  of  the  Royal  Society,  and  some 
time  later  he  was  appointed  Secretary,  an  office  which  he 
held  until  he  was  made  Astronomer  Royal.  In  1679  he 
visited  Germany,  in  order  to  represent  the  Royal  Society 
in  a  controversy  with  Hevelius  of  Dantzig,  in  regard  to 
the  utility  of  the  telescope  in  the  determination  of  the 
positions  of  the  stars.  Halley  remained  at  Dantzig  with 
Hevelius  for  a  year,  and  spoke  highly  of  Hevelius1  skill  as 
an  observer.  In  1 680  Halley  travelled  over  Europe.  He 
spent  much  time  at  the  Paris  Observatory,  at  that  time 
directed  by  Cassini,  famous  for  his  satellite  discoveries. 
Halley  and  Cassini  made  observations  together  on  the 
comet  of  1680.  The  English  astronomer  was  very  well 
received  in  Paris  and  in  all  the  continental  cities.  Halley 
was  much  interested  in  the  subject  of  magnetism  and  the 
variation  of  the  magnetic  needle.  In  1692  he  put  for- 
ward a  theory  of  terrestrial  magnetism.  Twice  he  took  a 
voyage  to  the  southern  seas  to  observe  this  variation.  In 
1694  he  set  out,  but  he  was  obliged  to  return  in  1695  as 
one  of  his  lieutenants  mutinied.  In  1699  he  again  set 
out,  and  passed  the  52nd  degree  of  latitude.  "  In  these 
latitudes,"  he  said,  "  we  fell  in  with  great  islands  of  ice  of 
so  incredible  height  and  magnitude,  that  I  scarce  dare 
write  my  thoughts  of  it."  The  ice  preventing  his  advance, 
he  finally  returned  to  England  in  1700,  and  published  a 
chart  respecting  magnetic  variation. 

302 


NEWTON   AND   HIS   SUCCESSORS 

In  1684  Halley  became  intimate  with  Newton,  and 
indeed  it  was  he  who  advised  Newton  to  publish  his  dis- 
coveries in  regard  to  gravitation.  In  December  1684 
Halley  announced  to  the  Royal  Society  that  Newton  was 
about  to  write  a  paper  on  the  subject  of  gravitation.  As 
has  been  already  explained,  the  Royal  Society  was  at  a 
very  low  ebb  in  regard  to  funds.  At  length  the  Society 
ordered  that  Halley  "  should  undertake  the  business  of 
looking  after  the  book  and  printing  it  at  his  own  charge," 
which  he  agreed  to  do. 

Reference  has  been  made  in  the  chapters  on  comets  to 
Halley's  greatest  discovery,  that  of  the  revolution  of  the 
comet  bearing  his  name.  Another  of  his  great  discoveries 
related  to  the  transit  of  Venus.  He  saw  that  the  transits 
would  give  astronomers  an  opportunity  of  measuring  the 
distance  of  the  Sun  from  the  Earth,  and  he  urged  on 
astronomers  the  necessity  of  observing  the  transit  of  1761, 
which,  however,  he  knew  could  not  occur  until  many  years 
after  his  death.  His  advice  was  taken  by  other  eminent 
astronomers  who  followed  him.  In  1715  Halley  observed 
the  total  eclipse  of  that  year,  the  first  which  was  visible 
in  London  since  1140.  He  observed  the  eclipse  from  the 
rooms  of  the  Royal  Society,  and  left  a  minute  description 
of  the  corona. 

The  death  of  Flamsteed,  which  took  place  in  1719, 
gave  Halley  the  position  of  Astronomer  Royal,  to  which 
he  was  appointed  in  1720.  He  found  no  instruments  in 
the  Observatory  at  Greenwich,  as  those  hitherto  in  use, 
being  the  property  of  Flamsteed,  had  been  removed  by 
*  his  wife,  who  refused  to  sell  them  to  Halley  on  account 
of  unhappy  differences  which  existed  between  the  two 
astronomers.  Not  only  had  Halley  no  instruments,  but 
he  was  also  without  assistance.  In  1721  he  had  a 

303 


NEWTON   AND   HIS   SUCCESSORS 

telescope  erected  at  Greenwich,  and  then,  though  sixty-four 
years  of  age,  he  determined  to  observe  the  Moon  during  a 
period  of  eighteen  years.  Halley  just  lived  to  complete 
his  observations,  which  were  very  useful.  His  health  began 
to  give  way  in  1739,  and  he  died  in  1742,  at  the  age  of 
eighty-five,  having  survived  Newton  for  fifteen  years.  He 
was  buried  at  Lee,  in  Kent. 

James  Bradley  and  James  Ferguson,  the  remaining  two 
men  of  note  among  Newton's  immediate  successors,  were 
each  men  of  distinction  in  their  particular  spheres.  James 
Bradley  was  born  at  Sherborne  in  Gloucestershire  in  1693. 
Of  his  private  life  there  is  little  to  tell.  He  was  educated 
first  at  the  school  of  Northleach,  and  afterwards  at  the 
University  of  Oxford,  which  he  entered  in  1711,  when  in 
his  nineteenth  year.  While  at  the  University  he  spent 
much  time  with  his  uncle,  the  Rev.  James  Pound,  who, 
although  by  profession  a  clergyman,  was  deeply  interested 
in  astronomy  and  was  a  well-known  observer.  It  was 
doubtless  through  friendship  with  his  uncle  that  Bradley 
became  expert  in  the  use  of  astronomical  instruments. 
Bradley  and  his  uncle  together  investigated  the  subject  of 
the  parallax  of  the  Sun  by  observing  the  opposition  of 
Mars.  Pound  and  Bradley  showed,  as  they  believed,  that 
the  distance  of  the  Sun  must  be  more  than  94  millions  of 
miles  and  less  than  125  millions.  We  now  know  that 
they  over-estimated  the  Sun's  distance ;  but,  considering 
their  imperfect  instruments,  it  was  remarkably  near  the 
truth.  Halley  had  evidently  a  high  opinion  of  Bradley, 
whose  talents  were  now  so  widely  known  that  he  was 
elected  a  Fellow  of  the  Royal  Society  in  1718.  About 
this  time  Bradley  paid  much  attention  to  the  eclipses  of 
Jupiter's  satellites,  which  he  predicted  with  much  accuracy. 

Bradley  was  originally  intended  for  a  clerical  career, 
304 


NEWTON   AND   HIS   SUCCESSORS 

and  in  1719  the  Bishop  of  Hereford  offered  him  the 
vicarage  of  Bridstow  in  Monmouthshire,  to  which  he  was 
appointed  in  1720.  But  he  was  only  two  years  in  his 
clerical  position.  The  Savilian  Professorship  of  Astronomy 
at  Oxford — previously  occupied  by  Halley — became  vacant 
by  the  death  of  Halley 's  successor,  Keill.  At  that  time  it 
was  a  rule  that  the  Savilian  Professor  of  Astronomy  must 
not  hold  a  clerical  appointment,  and  there  is  little  doubt 
that  Pound  would  have  been  elected  had  he  been  willing 
to  surrender  his  connection  with  the  Church.  Bradley, 
however,  expressed  his  willingness  to  give  up  his  vicarage, 
and  he  was  appointed  to  the  Savilian  Chair  in  1722,  when 
he  was  twenty-nine  years  of  age.  Notwithstanding  the 
awkward  and  inconvenient  instruments  with  which  the 
Savilian  Professor  had  to  conduct  his  observations,  in 
1723  he  observed  the  transit  of  Mercuiy,  and  succeeded 
in  measuring  the  size  of  Venus ;  while  he  made  many 
important  observations  on  the  comet  of  1723. 

The  greatest  of  Bradley 's  discoveries  was  made  in  1725 
and  1726.  He  was  looking  for  something  quite  different 
from  what  he  discovered.  From  the  time  of  Copernicus, 
astronomers  had  made  every  effort  to  measure  the  parallax 
of  the  stars,  and  their  inability  to  do  so  was  long  felt  as 
the  one  drawback  to  the  Copernican  system.  Bradley 
made  an  attempt.  He  was  not  successful,  but  his  labours 
were  rewarded  by  a  brilliant  discovery — that  of  the  "  aber- 
ration of  light."  The  astronomer  decided  to  make  ob- 
servations for  a  year  on  the  star  Gamma  Draconis,  in  the 
constellation  Draco,  the  instrument  used  being  a  refractor 
*  24  feet  3  inches  in  focal  length.  It  was  erected  in  Kew 
Green,  near  London,  at  the  house  occupied  by  Samuel 
Molyneux,  afterwards  a  Lord  of  the  Admiralty,  who  at 
one  time  was  greatly  interested  in  astronomy.  The 

305  u 


NEWTON   AND   HIS   SUCCESSORS 

observations  in  search  of  parallax  were  continued  for  a 
year.  It  was  found,  after  much  patient  observation,  that 
Gamma  Draconis  was  actually  displaced  in  position.  But 
Bradley  was  not  long  in  finding  that  the  displacement 
was  not  due  to  parallax,  as  it  was  of  an  exactly  opposite 
character.  For  a  long  time  the  astronomer  was  much 
perplexed  as  to  the  cause  of  the  variation,  and  he  deter- 
mined to  make  elaborate  investigation  of  various  other 
stars.  He  found  that  all  the  stars  which  he  observed 
showed  the  same  displacement. 

This  phenomenon  was  not  explained  by  Bradley  until 
some  time  after  the  remarkable  discovery.  It  had  been 
discovered  before  the  time  of  Bradley,  by  Roemer,  that  light 
requires  time  to  travel  through  space,  and  it  was  found 
that  the  rate  at  which  it  travelled  was  186,000  miles  a 
second.  Bradley  then  hit  upon  the  idea  that  the  reason 
of  the  displacement  was  the  combined  movements  of  light 
and  the  Earth.  Thus,  as  the  Earth  moved,  the  stars 
were  displaced  in  position.  This  discovery  finally  con- 
firmed the  Copernican  theory  by  showing  that  the  Earth 
really  moved,  and  it  was  also  of  great  use  in  astronomy. 
Bradley  made  many  experiments  to  verify  his  discovery, 
which  was  soon  placed  beyond  all  doubt.  This  discovery 
gained  for  Bradley  the  admiration  of  Newton,  who,  in  his  old 
age,  was  heard  to  call  him  "the  best  astronomer  in  Europe." 

In  February  1742  Bradley  was  appointed  Astronomer 
Royal  of  England  in  succession  to  Halley.  In  June  1 742 
he  made  his  first  observation  with  the  transit  instrument 
at  Greenwich.  The  new  Astronomer  Royal  was  an  ex- 
tremely energetic  man,  and  it  appears  that  on  one  day 
255  observations  were  taken  by  himself  alone.  By  1747 
he  had  completed  the  observations  which  revealed  his 
second  great  discovery,  that  of  the  nutation  of  the 

306 


NEWTON  AND   HIS   SUCCESSORS 

Earth's  axis.  It  had  been  known  for  long  that  the  pole 
of  the  Earth  is  not  fixed,  and  does  not  point  constantly  to 
the  same  point  in  the  sky.  Thus,  the  star  in  Ursa  Minor 
which  we  call  the  Pole  Star  will  not  occupy  that  position 
for  ever.  In  the  course  of  25,000  years  the  pole  will 
have  moved  in  a  great  circle  through  the  sky,  and  will 
once  more  point  to  the  Pole  Star.  During  its  revolution 
in  the  course  of  12,000  years  the  pole  will  be  close  to 
Vega  in  Lyra.  What  Bradley  discovered  was  that  in 
the  course  of  nineteen  years  the  position  of  the  pole  varied 
in  an  extraordinary  manner.  This  was  at  first  thought  to 
be  inconsistent  with  Newton's  theory,  but  Bradley  showed 
it  to  be  due  to  variable  action  of  the  Moon  on  the  matter 
accumulated  round  the  terrestrial  equator. 

In  1752  Bradley  took  a  prominent  part  in  the  change 
of  the  calendar  in  England.  Many  years  before,  the 
Gregorian  calendar  had  been  instituted  by  one  of  the 
Popes  and  adopted  by  many  of  the  countries  of  Europe. 
In  this  matter  the  Roman  Catholic  Church  happened  to 
be  right,  but  England  for  long  refused  to  accept  the  new 
calendar.  For  his  efforts  Bradley  met  with  violent  op- 
position. In  the  words  of  Mr.  Morton,  "the  people 
believed  that  the  astronomer  was  somehow  going  to  rob 
them  of  eleven  days  of  their  lives,  and  his  decline  and 
death  soon  after  was  popularly  supposed  to  be  the  judg- 
ment of  Heaven."  During  the  last  two  years  of  his  life 
he  was  subject  to  a  melancholy  depression,  as  he  feared 
that  he  would  survive  his  mental  powers.  Probably  this 
depression  hastened  his  death,  which  took  place  in  1762. 

Newton's  theory  of  gravitation,  despite  his  work  and 
that  of  his  successors,  was  not  at  first  popular,  especially 
in  England.  Strange  to  say,  England  was  not  the  first 
country  to  accept  the  Newtonian  teaching.  In  Scotland 

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NEWTON   AND   HIS   SUCCESSORS 

the  law  of  gravitation  was  taught  earlier  than  in  the 
sister  kingdom,  and,  indeed,  it  fell  to  a  Scotsman  to 
popularise  fully  the  Newtonian  theory.  "Astronomy 
explained  upon  Sir  Isaac  Newton's  Principles"  was  the 
work  of  James  Ferguson. 

James  Ferguson  was  born  at  Core  of  Mayen,  near  Rothie- 
may  in  Banffshire,  in  1710.  His  father,  John  Ferguson, 
was  a  poor  farm  labourer,  and  James  was  the  second  son. 
The  future  astronomer  had  little  education.  He  learned 
to  read  unaided,  and  his  father,  a  man  of  considerable 
intelligence,  taught  him  to  write.  "  About  three  months 
I  afterwards  had  at  the  Grammar  School  at  Keith,"  wrote 
Ferguson,  "  was  all  the  education  I  ever  received." 

When  about  seven  years  of  age  he  became  interested  in 
mechanics,  and  wrote  an  account  of  mechanical  contrivances. 
At  the  age  of  ten  he  was  sent  by  his  father  to  keep  sheep 
for  a  neighbour.  While  so  employed  he  began  to  study 
the  stars.  When  he  was  fourteen  years  of  age  he,  to  give 
his  own  account,  "  went  to  serve  a  considerable  farmer  in 
the  neighbourhood,  whose  name  was  James  Glashan.  I 
found  him  very  kind  and  indulgent ;  but  he  soon  observed 
that,  when  my  work  was  over,  I  went  into  a  field  with  a 
blanket  about  me,  lay  down  on  my  back,  and  stretched  a 
thread  with  small  beads  upon  it  at  arm's  length  between 
my  eye  and  the  stars,  sliding  the  beads  upon  it  till  they 
hid  such  and  such  stars  from  my  eye  in  order  to  take  their 
apparent  distance  from  one  another,  and  then,  laying  the 
thread  upon  a  paper,  I  marked  the  stars  thereon  by  the 
beads  according  to  their  respective  positions,  having  a  candle 
by  me.  My  master  at  first  laughed  at  me,  but  when  I  ex- 
plained my  meaning  to  him,  he  encouraged  me  to  go  on  ; 
and  that  I  might  make  fair  copies  in  the  daytime  of  what 
I  had  done  in  the  night,  he  often  worked  for  me  himself." 

308 


NEWTON  AND   HIS   SUCCESSORS 

Thus  in  the  lonely  hills  of  Banffshire  the  shepherd  boy 
astronomer,  encouraged  by  this  kindly  farmer,  commenced 
observation  of  the  great  orbs  of  heaven. 

Through  Glashan,  Ferguson  became  acquainted  with 
higher  people  about  Banffshire,  and  lived  for  a  time  with 
Thomas  Grant,  a  neighbouring  gentleman,  whose  butler 
encouraged  him  in  his  studies.  This  man  was  evidently  a 
good  mathematician,  and  he  taught  Ferguson  algebra  and 
geometry.  After  his  friend  left  the  gentleman's  house, 
Ferguson  went  back  to  live  with  his  father,  and  was  em- 
ployed by  a  miller  about  1731.  In  the  following  year 
Ferguson  became  acquainted  with  Sir  James  Dunbar  of 
Durn,  whose  sister,  being  much  interested  in  the  young 
astronomer,  took  him  with  her  to  Edinburgh  in  1734.  He 
remained  some  time  in  Edinburgh,  and  while  paying  a  visit 
to  Inverness  in  1739  he  again  became  interested  in  astro- 
nomy, and  constructed  on  paper  an  elaborate  diagram  of 
the  motions  of  the  Sun  and  Moon.  He  also  made  calcu- 
lations regarding  eclipses  of  the  Sun. 

Ferguson  returned  to  Edinburgh  in  1741,  and  two  years 
later  finally  quitted  Scotland  for  London,  taking  along  with 
him  a  mechanical  "  orrery  "  representing  the  movements  of 
the  planets,  which  he  constructed  in  Edinburgh.  On  his 
arrival  in  London,  the  astronomer  became  intimate  with  a 
gentleman  who  proposed  to  get  him  appointed  master  of 
a  mathematical  school.  The  plan,  however,  collapsed,  and 
Ferguson  took  up  the  business  of  drawing  pictures  and 
lecturing  on  astronomy.  In  the  words  of  Henderson, 
the  author  of  the  "  Life  of  Ferguson  " — "  with  these  two 
professions,  Ferguson  had  a  somewhat  severe  struggle  for 
a  living  in  London  for  nearly  seventeen  years." 

Although  James  Ferguson  was  a  great  observer,  he  was 
not  a  great  mathematician,  and  to  the  end  of  his  life  he 

309 


NEWTON  AND   HIS   SUCCESSORS 

did  not  understand  Euclid.  He  had,  however,  a  genius 
for  mechanical  invention,  and  he  constructed  a  large  number 
of  orreries,  planetariums,  etc.,  representing  the  motions  of 
the  Sun,  Moon,  planets,  and  comets.  These  mechanical 
models  were  highly  complex  in  their  structure,  and  we  may 
assert  that  no  astronomer  has  ever  possessed  such  a  genius 
for  representing  the  movements  of  the  celestial  bodies  by 
means  of  mechanical  contrivances  as  James  Ferguson.  He 
likewise  constructed  astronomical  clocks  and  sundials.  In 
fact,  everything  connected  with  observational  astronomy 
was  dealt  with  in  these  wonderful  machines.  In  1748 
Ferguson  commenced  his  popular  lectures,  the  first  subject 
being  the  solar  eclipse  of  July  1 4  in  that  year.  The  follow- 
ing year  he  lectured  on  other  subjects  besides  astronomy, 
including  mechanics,  electricity,  optics,  &c.  In  1751  he 
constructed  his  satellite  machine,  which  represented  by 
clockwork  the  motions  of  Jupiter's  satellites.  An  ex- 
cellent illustration  of  this  machine  is  given  in  Henderson's 
work,  to  which  reference  has  been  already  made. 

Ferguson  published  in  1 754  one  of  his  works,  "  An  Idea 
of  the  Material  Universe  from  a  Survey  of  the  Solar  System,1'1 
and  at  this  time  he  was  making  preparations  for  his  greatest 
book,  "  Astronomy  explained  upon  Sir  Isaac  Newton's 
Principles,"  which  was  published  in  London  in  June  1756. 
During  the  author's  lifetime  it  went  through  six  editions. 
Ferguson  was  now  held  in  universal  respect,  and  his  work 
superseded  for  a  great  number  of  years  all  other  books  on 
astronomy.  But  he  was  in  very  poor  circumstances,  his 
sole  livelihood  being  picture-drawing  and  his  lectures.  In 
1760  King  George  III.  granted  to  Ferguson  an  allowance 
of  £50  a  year.  This  pension  was  given  at  a  critical  period 
in  the  astronomer's  life,  when  his  difficulties  almost  made 
him  contemplate  returning  to  Scotland.  The  pension, 

310 


NEWTON  AND   HIS   SUCCESSORS 

however,  placed  him  in  a  fairly  prosperous  position,  and  he 
lectured  at  Bristol  and  at  Bath  with  great  popular  success. 
His  reputation  too  increased,  and  in  1763  he  was  elected  a 
Fellow  of  the  Royal  Society. 

In  1761  Ferguson  observed  the  transit  of  Venus  from  the 
top  of  the  British  Museum,  using  a  six-foot  reflector.  He 
remarked,  "  I  carefully  examined  the  Sun's  disc  to  dis- 
cover a  satellite  of  Venus  but  saw  none."  For  some  time 
before  the  transit  he  had  been  taking  much  interest  in 
it,  as  it  afforded  the  best  means  of  measuring  the  Sun's 
distance.  Two  years  later  he  sent  a  paper  on  his  observa- 
tions to  be  read  before  the  Royal  Society.  Year  after  year 
the  astronomer  invented  new  machines  representing  the 
movement  of  the  planets  to  be  exhibited  at  his  public 
lectures.  He  also  observed  the  spots  on  the  Sun,  and  left 
a  drawing  of  them,  while  in  1769  he  published  a  descrip- 
tion of  the  transit  of  Venus  of  that  year,  the  last  of  the 
pair  of  transits  visible  during  his  lifetime. 

Ferguson  died  in  London  in  1776.  His  name  will  for 
ever  be  remembered  as  one  who  not  only  made  important 
observations  and  constructed  extraordinary  instruments 
and  machines,  but  as  one  who  did  more  to  make  astro- 
nomy popular  than  any  astronomer  of  his  day.  The 
greatest  service,  however,  which  this  man  of  science 
rendered  was  that  it  was  his  book  on  astronomy  which 
started  William  Herschel  on  his  wonderful  career  as  an 
observer  of  the  heavens,  and  for  this  alone  the  world  can 
never  be  sufficiently  grateful.  But  the  chief  lesson  which 
we  learn  from  the  life  of  James  Ferguson  is  that  en- 
thusiasm and  perseverance  overcome  all  obstacles.  It 
is  surely  a  striking  fact  that  in  the  face  of  tremendous 
difficulties  the  humble  shepherd  boy  was  destined  to  do 
more  in  popularising  astronomy  than  all  his  predecessors. 

311 


CHAPTER   XXXII 

THE   CONQUEST   OF   THE   STARS 

IN  the  foregoing  pages  many  references  have  been 
made  to  the  immortal  name  of  William  Herschel, 
but  little  has  been  said  of  the  exact  position  which 
Herschel  occupies  in  Astronomy.  The  astronomers  before 
Herschel  occupied  themselves  only  with  the  solar  system 
— the  little  group  of  planets  moving  round"  the  Sun. 
Even  the  mighty  mind  of  Newton  was  obliged  to  con- 
centrate on  the  solar  system.  The  stars  were  observed 
certainly,  but  more  as  convenient  reference  points  for  the 
observation  of  the  Moon  and  planets  than  from  the  desire 
of  the  astronomers  to  learn  anything  of  the  stellar  orbs 
for  their  own  sake.  It  was  reserved  for  Herschel  to  com- 
mence the  conquest  of  the  stars,  to  start  astronomy  on  a 
new  path.  His  epitaph  claims  that  "he  broke  through 
the  barriers  of  the  skies  "  ;  and  it  is  no  exaggeration  to  say 
that  this  is  true.  He  stands  only  second  to  Newton  among 
the  pioneers  of  astronomy.  For  he  led  his  fellow  astro- 
nomers, we  might  say,  to  a  higher  pinnacle  of  knowledge 
than  had  ever  before  been  attained,  and  revealed  a  vista 
of  Infinity  and  Eternity  unthinkable  to  the  mind  of  man. 
Herschel  was  born  at  Hanover  on  November  15,  1738. 
He  was  the  third  son  and  fourth  child  of  Isaac  Herschel, 
originally  a  bandsman,  but  afterwards  the  bandmaster  of 
the  Hanoverian  Guards.  Although  in  humble  circum- 
stances, Isaac  Herschel  was  a  man  of  considerable  intelli- 

312 


THE  CONQUEST   OF  THE   STARS 

gence,  an  eminent  musician,  and  greatly  interested  in 
astronomy.  He  had  a  family  of  ten  children,  and  of  these 
William  was  by  far  the  most  accomplished.  He  and  his 
sister  Caroline,  who  was  twelve  years  his  junior,  were  the 
only  members  of  the  family  who  achieved  distinction.  From 
the  beginning  of  her  life  Caroline  was  deeply  attached  to 
her  father  and  her  brother  William,  who  were  the  only  two 
members  of  the  family  who  showed  her  invariable  affection. 
William  Herschel  attended  the  garrison  school  at 
Hanover  until  he  was  fourteen  years  of  age.  Here  he 
displayed  his  love  of  learning  and  his  brilliant  powers 
by  mastering  his  lessons  in  half  the  time  taken  by  his 
brother  Jacob,  his  senior  by  four  years.  William  Her- 
schel was  a  competent  musician,  and,  along  with  his 
brother,  became  an  oboist  in  the  Hanoverian  Guards, 
of  which  his  father  was  bandmaster.  The  outbreak  of 
the  Seven  Years'  War  in  1756  compelled  the  Hanoverian 
Guards  to  fight.  Conscription  being  the  rule,  the  musi- 
cians were  not  exempted  from  serving  their  country. 
After  the  defeat  of  the  English  and  the  Hanoverians  at 
Hastenbeck  in  1757,  William  Herschel  spent  the  night 
in  a  ditch,  and,  after  due  consideration,  decided  that 
fighting  would  not  be  his  profession.  In  fact,  with  the 
consent  of  his  father  and  mother,  he  deserted  and  sailed 
for  England,  where  he  arrived  when  in  his  nineteenth 
year.  For  some  time  he  wandered  through  England  in 
search  of  some  musical  employment,  and  in  1 760  he  was 
appointed  to  train  the  band  of  the  Durham  Militia.  Five 
years  later  he  became  organist  at  Halifax,  and  in  1767  in 
«the  Octagon  Chapel  at  Bath,  where  he  continued  until  he 
became  an  astronomer.  Herschel  in  1 764  paid  a  visit  to  his 
father,  who  was  now  failing,  and  who  died  in  1767.  His 
death  was  a  severe  blow  to  Caroline,  whose  affection  was 

313 


THE   CONQUEST   OF  THE   STARS 

concentrated  on  her  father  and  her  brother  William.  Her 
father  had  desired  to  give  her  a  good  education,  but  her 
mother  and  her  brother  Jacob  wished  her  to  learn  no  more 
than  was  necessary  for  the  education  of  a  housemaid.  After 
five  years  William  Herschel  decided  to  take  his  sister  with 
him  to  England,  and  she  arrived  in  Bath  in  August  1772. 
At  the  time  when  Caroline  Herschel  arrived  in  England 
her  brother  was  beginning  to  take  a  deep  interest  in 
astronomy.  After  conducting  a  concert  Herschel  would 
return  to  his  room  and  study  Maclaurin's  "  Fluxions  "  and 
Ferguson's  "Astronomy."  His  original  interest  in  the 
latter  science  was  due  to  his  father,  but  the  perusal  of  the 
work  of  Ferguson  aroused  a  fresh  desire  to  see  for  himself 
the  orbs  of  heaven.  As  Caroline  expressed  it :  "  It  soon 
appeared  that  my  brother  was  not  contented  with  knowing 
what  former  observers  had  seen. "  He  hired  a  small  telescope, 
and  was  so  charmed  with  the  wonders  of  the  heavens  that  he 
determined  to  have  an  instrument  for  himself.  He  there- 
fore wrote  to  London  to  make  inquiries.  But  the  price 
of  the  telescope  was  too  great  for  Herschel  with  his  limited 
means.  The  Bath  musician,  however,  was  not  the  man  to  be 
baffled  by  difficulties.  He  made  up  his  mind  to  make  his 
own  telescope,  and,  buying  the  apparatus  of  a  local  optician, 
he  succeeded  in  constructing,  after  many  failures,  a  reflector, 
the  mirror  of  speculum  metal.  On  his  icturn  from  a  con- 
cert he  would  plunge  with  enthusiasm  into  telescope  making, 
and,  while  grinding  and  shaping  the  mirror,  he  was  obliged  to 
hold  his  hands  on  it  for  sixteen  hours  at  a  time,  his  meals 
being  supplied  by  his  sister,  who  also  read  stories  to  him 
to  break  the  monotony.  But  for  Caroline  Herschel,  who 
spared  no  trouble  for  her  brother,  William  would  never 
have  become  the  famous  astronomer,  and  she  sacrificed  for 
his  sake  her  prospects  as  a  public  singer.  In  1774,  when 


THE   CONQUEST   OF  THE   STARS 

he  was  thirty-five  years  of  age,  Herschel  began  to  observe 
the  heavens  with  his  own  telescope. 

For  seven  years  Herschel  maintained  his  love  for  astro- 
nomy while  pursuing  the  profession  of  music.  Night  after 
night  he  swept  the  skies  with  various  telescopes.  Having 
made  one  instrument,  he  determined  on  seeing  more  of  the 
celestial  wonders,  and  constructed  larger  ones.  In  1779, 
through  the  friendship  of  Dr.  Watson,  an  eminent  literary 
man,  Herschel  entered  the  Literary  Society  of  Bath.  In 
the  following  year  he  sent  two  papers  to  the  Royal  Society, 
followed  by  another  in  January  1781.  But  an  event  took 
place  which  completely  changed  the  current  of  his  life. 
In  1780  he  began  a  review  of  the  heavens  with  a  6-inch 
Newtonian  reflector.  As  he  explored  the  constellation 
Gemini  on  the  night  of  March  13,  1781,  he  observed  an 
object  which,  unlike  the  stars,  showed  a  round  and  well- 
defined  disc,  the  motion  of  which  was  quite  perceptible. 
This  discovery  of  the  planet  Uranus,  mentioned  in  a  pre- 
vious chapter,  was  the  occasion  of  much  excitement.  The 
Bath  musician  was  at  once  raised  to  the  rank  of  an  illus- 
trious astronomer.  King  George  III.,  hearing  of  Her- 
schel's  discovery,  summoned  him  to  London  in  1782,  and 
conferred  on  him  the  title  of  King's  Astronomer,  with  the 
small  salary  of  ^200  a  year.  The  King  likewise  pardoned 
him  for  his  desertion  from  the  army  twenty-five  years 
previously.  Herschel  now  cut  himself  adrift  from  the  pro- 
fession of  music,  and  he  and  his  sister  settled  at  Datchet, 
near  Windsor,  in  August  1782.  He  was  then  forty-four 
years  of  age. 

*  William  and  Caroline  Herschel  removed  in  1786  to 
Slough,  near  Windsor — "  the  spot  of  all  the  world,"  wrote 
Arago,  "where  the  greatest  number  of  discoveries  have 
been  made  " — and  the  astronomer  remained  there  for  the 

315 


THE   CONQUEST   OF   THE   STARS 

rest  of  his  life.  From  dusk  to  dawn  he  swept  the  heavens 
with  his  mighty  reflectors,  in  the  mirrors  of  which  the  stars 
appeared  to  move  in  a  glorious  procession.  He  discovered 
many  star  clusters,  over  two  thousand  nebulae,  and  about 
seventy  million  stars.  In  1787  Caroline  Herschel  was 
appointed  his  assistant  with  a  salary  of  ^?50  a  year.  She 
would  sit  beside  her  brother,  who  would  dictate  to  her 
what  he  saw.  Sometimes,  she  tells  us  in  her  memoirs,  the 
ink  froze  in  her  pen.  Miss  Clerke  thus  describes  Her- 
schel's  enthusiasm  :  "  The  thermometer  might  descend 
below  zero,  ink  might  freeze,  mirrors  might  crack,  but 
provided  the  stars  shone  he  and  his  sister  worked  on  from 
dusk  till  dawn." 

"  While  Herschel  was  thus  rapidly  rising  into  fame," 
writes  Mr.  Si  me  in  his  admirable  biography  of  the  great 
German  astronomer,  "he  was  not  forgetful  of  the  sister 
who  so  generously  sacrificed  her  own  wishes  and  prospects 
as  a  singer  to  advance  his  as  an  astronomer."  He  pre- 
sented Caroline  with  a  five-foot  reflector,  with  which  she 
explored  the  skies.  She  discovered  a  number  of  clusters 
and  nebulae  and  detected  eight  comets — one  of  which 
is  now  known  as  Encke's — between  1786  and  1797.  Von 
Magellan,  a  foreign  astronomer,  reported  in  1786  that  the 
brother  and  sister  were  equally  interested  in  astronomy. 

The  University  of  Edinburgh  conferred  on  Herschel  in 
1786  the  degree  of  LL.D.  ;  in  1792  he  received  the  free- 
dom of  Glasgow,  and  in  1816  he  was  created  a  knight  of 
the  Royal  Hanoverian  Guelphic  Order.  Five  years  later 
he  became  the  first  President  of  the  Royal  Astronomical 
Society.  But  he  cared  little  or  nothing  for  honours.  He 
was  described  as  "  a  man  without  a  wish  that  has  its  ob- 
ject in  the  terrestrial  globe."  Like  Newton,  he  was  in  no 
way  elated  with  his  wonderful  discoveries.  Writing  to  his 

316 


THE   CONQUEST  OF   THE   STARS 

sister  from  London  in  1782  he  said,  "Among  opticians 
and  astronomers  nothing  now  is  talked  of  but  what  they 
call  my  great  discoveries.  Alas  !  this  shows  how  far  they 
are  behind,  when  such  trifles  as  I  have  seen  and  done  are 
called  great." 

Advancing  years  in  no  way  affected  HerscheFs  wonderful 
mind.  But  his  duties  as  King's  Astronomer  necessitated 
his  acting  as  what  Mr.  Sime  calls  "  showman  of  the  heavens  " 
on  the  visits  of  royalties  to  Windsor,  often  after  a  whole  day's 
work,  when  rest  was  absolutely  necessary.  This,  tremen- 
dous strain,  which  reflects  little  credit  on  the  Court,  proved 
too  much  for  the  old  man.  His  health  began  to  give  way, 
although  his  mind  was  as  vigorous  as  ever.  As  Miss  Clerke 
puts  it :  "  All  his  own  instincts  were  still  alive,  only  the 
bodily  power  to  carry  out  their  behests  was  gone.  An 
unparalleled  career  of  achievement  left  him  unsatisfied 
with  what  he  had  done.  His  strong  nerves  were  at  last 
shattered."  After  a  prolonged  period  of  failing  health 
he  died  at  Slough  at  the  age  of  eighty-three  on  August  25, 
1 822.  His  sister  survived  him  for  twenty-five  years,  dying 
early  in  1848  at  the  advanced  age  of  ninety-seven. 

The  son  of  the  Hanover  bandmaster  was,  in  the  truest 
sense,  the  founder  of  sidereal  astronomy.  He  observed 
the  suns  which  spangle  the  sky  to  discover  the  secrets  of 
their  constitution.  He  aroused  by  his  brilliant  discoveries 
widespread  interest  in  the  star  depths.  His  career  stimu- 
lated astronomical  research  during  the  nineteenth  century. 
This  may  be  seen  from  a  study  of  the  astronomical  work 
of  the  past  hundred  years.  The  great  work  of  Herschel 
"has  somewhat  overshadowed  his  successors,  many  of  whom 
have  been  men  of  the  most  brilliant  genius.  Contempo- 
rary with  him  were  such  men  as  Laplace  and  Gibers ; 
among  his  immediate  successors  we  find  the  great  names 

317 


THE  CONQUEST  OF  THE   STARS 

of  Bessel,  Struve,  and  Henderson ;  in  the  middle  of  the 
century  Le  Verrier  and  Adams ;  while  in  more  recent 
times  the  astronomical  army  has  been  led  to  still  greater 
triumphs  by  such  men  as  Secchi,  Huggins  and  Vogel, 
Schiaparelli  and  Newcomb,  and  many  other  devoted 
students  of  Nature.  Thus,  while  the  Romance  of  Astro- 
nomy belongs  in  the  first  place  to  the  heavenly  bodies 
themselves,  there  is  something  no  less  romantic  in  the 
study  of  the  labours  of  that  noble  band  of  men  who  have 
dared  to  sound  the  Universe  and  conquer  the  unknown. 


318 


CHAPTER    XXXIII 
A   FINAL   SURVEY 

IN  the  preceding  chapters  we  have  dealt  with  the 
Universe  as  we  know  it  to-day,  and  with  the  means 
by  which  astronomers  have  reached  their  conclusions. 
The  science  of  astronomy  is  in  many  ways  the  grandest  of 
all  the  sciences,  for  it  has  enlarged  our  knowledge  a  thou- 
sand-fold, a  million-fold,  beyond  all  the  other  sciences. 
It  leads  us  to  look  outwards  by  means  of  the  telescope  and 
the  spectroscope  into  mighty  vistas  in  space,  and  to  look 
backwards  in  imagination  over  enormous  vistas  of  time. 
Schiaparelli  has  called  astronomy  the  science  of  Infinity 
and  Eternity,  and  this  phrase  exactly  describes  the  modern 
development  of  the  science  of  the  heavens.  On  all  sides 
the  astronomer  deals  with  the  Infinite  and  the  Eternal. 

The  romance  of  modern  astronomy  consists  in  great 
part  in  the  enormous  extension  of  our  knowledge  of  the 
visible  Universe.  As  a  distinguished  writer  has  well 
said,  "Compared  with  the  fields  from  which  our  stars 
fling  us  their  light,  the  Cosmos  of  the  ancient  world  was 
but  as  a  cabinet  of  brilliants,  or  rather  a  little  jewelled 
cup  found  in  the  ocean  or  the  wilderness.  Wonderful  as 
were  the  achievements  and  sagacious  as  were  the  guesses 
of  the  Greek  astronomers,  they  little  suspected  what  they 
were  registering  when  they  drew  up  their  catalogues  of 
stars."  To  the  ancients  the  Earth  was  the  centre  of 
the  Universe,  fixed  and  immovable,  the  end  and  aim  of 

319 


A  FINAL   SURVEY 

the  entire  creation.  Round  the  Earth  revolved  the  Moon, 
the  Sun,  the  planets,  each  in  their  own  particular  com- 
plicated pathways,  and,  farther  away,  the  fixed  stars,  which 
they  believed  to  be  points  of  light  fastened  to  the  inside 
of  a  sphere.  What  lay  beyond  was  outside  the  Universe. 
The  whole  Universe  was  supposed  to  be  small  in  extent ;  its 
size  was  quite  easily  grasped  by  the  mind  of  man.  The 
Universe,  too,  in  the  opinion  of  the  ancients,  was  created 
purely  for  the  benefit  of  the  Earth's  inhabitants,  the 
Sun  to  give  light  and  heat,  and  the  Moon  to  illuminate 
the  nights,  while  the  stars  were  regarded  as  convenient 
secondary  light-givers  in  the  absence  of  the  Moon. 

What  a  contrast  between  these  views  and  the  truths 
with  which  we  are  acquainted  to-day  through  modern  astro- 
nomy. So  far  from  being  the  centre  of  the  Universe,  the 
Earth  is  not  even  the  centre  of  the  planetary  system ;  so 
far  from  being  the  largest  and  most  important  body  in 
the  Universe,  it  is  merely  what  we  might  call  the  second- 
rate  satellite  of  a  second-rate  star.  So  far  from  the 
dimensions  of  the  Universe  being  conceivable,  they  are 
absolutely  inconceivable.  The  solar  system  alone  is  nearly 
five  thousand  millions  of  miles  in  diameter,  and  the  solar 
system  is  a  mere  point  in  comparison  with  the  greater 
system  of  the  stars. 

No  less  remarkable  than  the  enlargement  of  the  Universe 
in  space  has  been  its  enlargement  in  time.  To  the  thinkers 
of  the  Middle  Ages  a  few  thousand  years  contained  the 
life  history  of  the  Universe.  Stars  and  Suns  were  all 
brought  into  existence  six  thousand  years  ago.  Beyond 
nothing  was  known.  Modern  astronomy  has  pushed  back 
the  beginning  of  things  into  the  vista  of  the  past.  Millions 
of  years,  tens  of  millions  of  years,  take  the  place  of  thou- 
sands. By  observations  on  the  heavens,  by  reasoning  on 

320 


A  FINAL   SURVEY 

these  observations,  astronomers  trace  processes  which  re- 
quire millions  of  years  for  their  completion.  Astronomy 
is  indeed  the  science  of  Eternity.  Not  only  so,  it  shows 
that  there  is  in  reality  no  such  thing  as  time,  that  it  is  a 
purely  relative  conception,  due  to  our  position  on  a  little 
planet  revolving  round  a  star. 

Our  subject  in  the  preceding  pages  has  been  the  romance 
of  modern  astronomy,  and  nothing  could  be  more  romantic 
than  the  steady  development  of  our  knowledge,  till  to-day 
we  know  the  Universe,  not  as  the  little  "  corner  "  which  it 
appeared  to  our  forefathers,  but  as  Infinity  itself.  A  brief 
survey  may  be  taken  of  the  journey  which  we  have  tra- 
versed in  imagination  in  the  preceding  pages.  Naturally 
the  mind  of  man,  in  its  journey  through  the  Infinite, 
begins  with  the  Earth,  our  dwelling-place.  By  the  re- 
velations of  astronomy,  we  behold  the  Earth  as  a  globe 
rotating  rapidly  on  its  own  axis,  and  in  ceaseless  revolu- 
tion round  the  Sun,  on  whose  beams  it  depends  for  its 
existence  as  an  abode  of  life. 

At  a  distance  of  238,000  miles  we  come  upon  our  faith- 
ful satellite  the  Moon,  the  only  one  of  the  celestial  bodies 
which  revolves  round  the  Earth.  The  Moon  is  the  Earth's 
peculiar  possession.  As  has  been  seen,  it  is  a  "  detached 
continent,"  probably  literally  as  well  as  metaphorically. 
And  we  perceive,  too,  that  the  life  of  the  Moon  as  a  world 
is  long  since  ended ;  it  is  a  closed  chapter  in  the  book  of 
time.  Modern  astronomy  shows  us  that,  as  Flammarion 
puts  it,  "  in  space  there  are  both  cradles  and  tombs."  The 
Moon  is  one  of  the  tombs  of  the  Universe. 

Then  our  study  of  the  Earth  and  Moon  shows  that  the 
*Earth  and  Moon  form  by  themselves  a  little  system — the 
Earth-Moon  system  or  Terrestrial  system,  as  it  is  variously 
called — within  the  greater  solar  system.  In  the  Earth- 

321  x 


A   FINAL   SURVEY 

Moon  system  our  scale  of  measurement  is  thousands  of 
miles ;  in  the  solar  system  we  have  to  measure  by  a  new 
scale — millions  of  miles.  In  the  middle  of  the  system  we 
see  the  mighty  Sun,  whose  diameter  is  a  hundred  times 
that  of  the  Earth,  rotating  slowly  on  its  axis  and  holding 
sway  over  a  system  of  planets  of  all  sizes,  and,  in  addition, 
controlling  the  motions  of  the  comets  and  meteoric  systems. 
Examples  have  been  given  of  the  power  of  the  Sun,  of  the 
storms  raging  in  its  atmosphere,  of  the  sea  of  fire  which 
surrounds  it,  and  of  the  atmospheric  catastrophes  which 
give  rise  to  the  mighty  spots  or  rents  in  the  glowing  atmos- 
phere. Reasoning  has  shown  us  the  enormous  age  of  the 
Sun — that  millions  of  years  may  elapse  and  make  little 
change  on  the  orb  of  day.  So  far  as  the  inhabitants  of 
the  Earth  are  concerned,  the  Sun  is  eternal. 

Round  the  Sun  we  see  revolving  the  planets,  divided 
into  the  three  well-defined  groups.  First,  we  have  the 
inner  planets,  of  which  our  Earth  holds  the  proud  position 
of  chief  world,  revolving  at  distances  which  vary  from  36 
millions  to  141  millions  of  miles.  This  group  includes  swift 
little  Mercury,  whirling  round  the  Sun  with  an  enormous 
velocity,  followed  by  Venus,  then  the  Earth,  and  next 
Mars.  Next  we  have  the  asteroids,  the  miniature  worlds 
which  fill  the  space  between  the  pathways  of  Mars  and 
Jupiter.  Thirdly  we  have  the  outer  planets,  revolving  at 
distances  varying  from  484  millions  to  2700  millions  of 
miles — Jupiter  with  its  retinue  of  eight  satellites,  Saturn 
with  its  more  wonderful  system  of  ten  attendant  worlds 
and  three  revolving  rings,  Uranus  with  its  four  moons, 
creeping  along  at  a  comparatively  leisurely  pace,  and, 
finally,  distant  Neptune,  the  exile  of  the  solar  system, 
circling  round  the  known  boundaries  of  the  solar  system 
with  one  faint  attendant.  Across  this  enormous  system, 

322 


A  FINAL   SURVEY 

with  a  diameter  of  over  five  thousand  millions  of  miles, 
the  rays  of  light  flash  in  eight  hours.  How  vast  is  the 
system,  how  unthinkable  are  its  dimensions,  how  unfathom- 
able its  depths  ;  and  how  wonderfully  is  it  regulated  by  that 
Divine  Ordinance  of  Nature,  the  law  of  gravitation. 

To  the  mind  of  the  ancient  astronomers  a  system  so 
vast,  as  we  know  the  solar  domain  to  be,  would  have  seemed 
Infinity  itself.  They  would  have  been  unable  to  conceive 
so  great  a  revelation  of  Immensity.  Yet,  when  we  come 
to  study  the  stars,  a  new  truth  dawns  on  our  minds  that 
just  as  the  Earth  and  Moon  form  by  themselves  a  little 
system  within  the  greater  solar  system,  so  the  solar  system 
itself,  containing  many  lesser  systems,  is  also  but  a  little 
system  within  a  greater — the  system  of  the  stars.  In  the 
Earth-Moon  system  the  scale  is  thousands  of  miles.  In 
dealing  with  the  solar  system  we  are  obliged  to  use  a  new 
scale — a  scale  of  millions  of  miles  ;  and  when  we  come  to 
consider  the  universe  of  the  stars,  this  scale  itself  is  quite 
inadequate.  The  scale  is  one  of  billions  and  hundreds  of 
billions  of  miles. 

So,  too,  in  regard  to  the  motion  of  light,  a  second  and 
a  half  is  required  for  light  to  pass  from  the  Moon  to  the 
Earth.  The  scale  of  light-velocity  for  the  Earth-Moon 
system  is  seconds.  For  the  solar  system  that  scale  is 
minutes  and  hours,  and  for  the  stellar  system  years  and 
centuries. 

In  his  "  Popular  Astronomy  "  Flammarion  brings  home 
very  vividly  the  isolation  and  minuteness  of  the  solar  system 
in  the  greater  system  of  the  stars.  On  a  journey  through 
space  in  imagination  the  French  astronomer  writes  :  "  The 
Sun  himself,  with  all  his  immense  system,  has  sunk  in  the 
Infinite  night.  On  the  wings  of  inter-sidereal  comets  we 
have  taken  our  flight  towards  the  stars,  the  suns  of  space. 

323 


A  FINAL   SURVEY 

Have  we  exactly  measured,  have  we  worthily  realised  the 
road  passed  over  by  our  thoughts  ?  The  nearest  star  to 
us  reigns  at  a  distance  of  about  twenty-five  billions  of  miles ; 
out  to  that  star  an  immense  desert  surrounds  us  the  most 
profound,  the  darkest  and  the  most  silent  of  solitudes.  The 
solar  system  seems  to  us  very  vast ;  relatively  to  the  fixed 
stars,  however,  our  whole  system  represents  but  an  isolated 
family  immediately  surrounding  us  :  a  sphere  as  vast  as  the 
whole  solar  system  would  be  reduced  to  the  size  of  a  simple 
point  if  it  were  transported  to  the  distance  of  the  nearest 
star.  The  space  which  extends  between  the  solar  system 
and  the  stars,  and  which  separates  the  stars  from  each  other, 
appears  to  be  entirely  void  of  visible  matter,  with  the 
exception  of  nebulous  fragments,  cometary  or  meteoric, 
which  circulate  here  and  there  in  the  immense  void.  Nine 
thousand  two  hundred  and  fifty  systems  like  ours  would  be 
contained  in  the  space  which  isolates  us  from  the  nearest 
star." 

When  we  come  to  contemplate  the  system  of  the  stars, 
to  journey  through  it  in  imagination,  we  see  our  Sun  from 
a  new  point  of  view.  It  is  merely  a  star  moving  through 
space,  and  carrying  with  it  planets,  satellites,  and  comets. 
All  the  stars  are  in  motion,  some  rushing  through  space 
with  almost  inconceivable  velocity,  others  moving  at  a 
slower  pace,  but  all  rushing  onwards  at  a  speed  to  which 
we  on  Earth  are  quite  unaccustomed.  There  are  in  the 
system  of  the  stars,  so  far  as  we  know,  about  500  million 
stars.  In  addition  to  those  bodies  modem  astronomy  has 
revealed  to  us  thousands  of  the  luminous  masses  known  as 
nebulae,  which  form  the  materials  out  of  which  finished 
systems  of  suns  and  planets  are  wrought  by  the  Divine 
power  in  the  course  of  ages.  Then  astronomy  shows  us 
the  possible  shape  of  the  starry  system.  It  tells  us  of  the 

324 


A  FINAL  SURVEY 

Galaxy,  that  mighty  region  of  clustering  orbs,  the  equator  of 
the  starry  globe,  and  it  indicates  that  the  starry  system,  like 
the  solar  system  and  the  smaller  satellite  systems,  is  merely 
a  system  within  a  greater.  But  what  that  greater  system 
consists  of  and  how  far  it  extends  the  mind  of  man  cannot 
tell.  Even  of  this  mighty  system  of  the  stars  itself  our 
knowledge  is  limited ;  we  do  not  know  whether  or  not  it 
has  a  central  body  ;  we  do  not  know  the  precise  distance  to 
which  it  extends ;  we  only  can  say  that  the  more  dis- 
tant stars  of  the  Milky  Way  are  placed  at  a  distance  so 
great  that  it  is  almost  impossible  to  express  them  on  the 
scale  of  miles.  On  the  scale  of  light  we  can  estimate  that 
the  light  rays  which  dart  from  the  Moon  in  a  second  and 
a  half,  and  cross  the  diameter  of  the  solar  system  in  eight 
hours,  require  thousands  of  years  to  span  the  mighty 
void. 

The  romance  of  astronomy  can  guide  us  no  further. 
On  the  threshold  of  a  vaster  system  we  pause,  and  only 
speculation  and  theory  can  take  us  beyond ;  but  how  vast 
a  field  of  space  has  modern  astronomy  revealed  to  us ! 
"  Eternity,"  says  Flammarion,  "  is  the  field  of  the  Eternal 
Sower."  Throughout  space  we  behold  stars  and  systems  in 
every  stage  of  evolution,  nebulous  masses,  clustering  stars, 
finished  suns  and  systems,  decrepit  worlds,  and,  finally, 
dead  and  dark  stars.  The  Eternal  Purpose  of  Evolution 
is  at  work  throughout  the  depths  of  space.  The  Divine 
Will  is  in  constant  operation  while  suns  and  systems  are 
being  fashioned  and  nebulous  matter  being  brought  into 
new  existence. 

.  What  a  vast  and  mighty  Universe  modern  astronomy 
reveals  to  the  mind  of  man,  a  Universe  without  bounds, 
without  beginning  or  end  in  time,  a  Universe  in  which  the 
Earth  is  but  an  absolutely  insignificant  atom,  "  a  globule 

325 


A  FINAL  SURVEY 

lost  in  the  Infinite  night."  As  Flammarion  puts  it,  "  In 
the  eternity  of  duration  the  life  of  our  proud  humanity, 
with  all  its  religious  and  political  history,  the  whole 
life  of  our  entire  planet  is  but  the  dream  of  a 
moment.1'* 

It  is  at  this  point,  the  last  of  the  great  truths  which  we 
learn  from  the  romance  of  astronomy,  that  the  minds  of 
many  get  disturbed.  Some  sigh  for  the  old  ideas  of  a 
compact  Universe  and  a  history  of  a  few  thousand  years, 
thinking  it  more  conducive  to  religious  faith ;  others  by 
accepting  these  sublime  truths  believe  their  faith  shaken 
by  the  marvels  which  science  has  revealed.  These  atti- 
tudes are  both  mistaken  ones.  Although  the  romance  of 
astronomy  ends  when  the  most  distant  star  is  reached, 
it  has  some  bearing  on  the  greater  problems  and  the  higher 
thought  of  men.  Modern  astronomy  has  revealed  to  us  a 
Universe  infinitely  vaster  than  was  known  to  our  fore- 
fathers ;  it  has  correspondingly  widened  and  exalted  our 
knowledge  of  the  Creator  of  all  things.  Not  only  has 
modern  astronomy  done  this,  it  has  also  shown  the  mar- 
vellous height  which  may  be  reached  by  the  human  mind, 
chained  to  a  little  revolving  globule  lost  in  the  rays  of  a 
star,  yet  able  to  span  the  vast  spaces  of  the  Universe,  to 
weigh  the  stars,  to  predict  the  celestial  motions ;  it  has 
given  us  a  deeper  appreciation  of  the  dignity  of  the  human 
intellect  which  can  soar  above  its  environment  into  the 
regions  of  things  divine  and  eternal. 

We  read  much  in  the  Bible  of  the  Infinite  and  the 
Eternal,  chiefly  as  attributes  of  God.  Astronomy  gives 
examples  of  Infinity  and  Eternity  and  leads  us  to  a 
higher  plane  of  thought  and  of  religion.  The  romance 
of  astronomy  is  more  romantic  than  any  romance,  more 
fascinating  than  any  story.  By  its  means  we  are  brought 


A   FINAL   SURVEY 

face  to  face  with  Infinity  and  Eternity,  and  after  a  study 
of  the  wonders  which  it  reveals  to  us,  we  can  only  repeat 
with  deeper  reverence  the  words  of  the  Psalmist : — 

"  Thine,  O  Lord,  is  the  greatness,  and  the  power,  and 
the  glory ;  for  all  in  heaven  and  earth  is  Thine." 


327 


INDEX 


A 

Adams,  J.  C.,  126,  127,  129,  163, 

317 

Aerolites,  164,  165,  166 
Airy,  Sir  G.  B.,  126,  127 
Alcyone,  206,  213 
Aldebaran,  185,  191,  192,  206,  260 
Algol,  199,  200,  203,  259 
Altair,  192,  256 
Anaxagoras,  219 
Anderson,  T.  D.,  197,  217 
Andromeda,  196,  214,  217,  255 
Andromeda,  nebula  in,  214,  215, 

216,  255 

Antares,  192,  203 
Aquarius,  256 

Aquila,  185,  219,  253,  255,  256 
Arago,  F.,  315 
Arcturus,  185,  189,  192,  193,  209, 

249,  256 

Argelander,  F.  W.  A.,  213 
Argus,  Eta,  198 
Aries,  185,  201,  256 
Aristotle.  19,  219,  273,  274,  275, 

281,  284 

Asteroids,  the,  61,  98-105,  322 
Astrsea,  101 

Auriga,  184,  190,  197,  219,  256 
Aurora  Borealis,  32,  57 

B 

Ball,  Sir  R.,  18,  48,  66,  82,  134, 
161,  211,  217,  221,  265 

Barnard,  E.  E.,  104,  105,  108,  113, 
138,  153,  220,  268 

Beer,  W.,  85 

Belts  of  Jupiter,  107,  108,  110, 
234 

Berlin  Observatory,  128 

Bessel,  F.  W.,  184,  202,  317 


Betelgeux,  191,  192,  256,  257,  259 

Bianchini,  79,  262 

Biela,  J.,  154 

Biela's  Comet,  139,  140,  154,  155 

156,  164 

Birmingham,  J.,  195 
Bode,  J.  E.,  98,  99,  100,  124 
Bode's  Law,  98 
Bootes,  184,  193,  255,  256 
Bouvard,  A.,  125 
Bradley,  J.,  187,  304-307 
Brahe,  Tycho,  23,  187,  194,  274, 

278-282,  287,   289,  290,   293, 

300 

Brashear,  Prof.,  102 
Bredikhine,  T.  A.,  109,  151,  152 
Brewster,  Sir  D.,  215 
Brooks'  Comet,  139,  153 
Brorsen's  Comet,  138,  139 
Bruno,  G.,  23,  283 
Burnham,  S.  W.,  203,  268 


Campbell,  W.  W.,  173,  176,  268 
Canals  of  Mars,  86-95 
Cancer,  206,  256 
Cancri,  Zeta,  205 
Canes  Venatici,  216,  256 
Canis  Major,  219,  255,  256 
Canis  Minor,  257 
Cape  Observatory,  146,  272 
Capella,  190,  192,  198,  256 
Capricorni,  Alpha,  201,  257 
Capricornus,  257 
Carlyle,  T.,  250,  251,  273 
Carnegie,  Dr.  A.,  268 
Carnegie  Observatory,  268,  269 
Cassini,  G.  D.,  79,  262,  302 
Cassiopeia,  184,  194,  219,  255,  257, 

280 
Castor,  202,  258 


328 


INDEX 


Celoria,  G.,  224 

Centauri,  Alpha,    187,    188,   193, 

202,  210 

Centauri,  Omega,  206 
Centaurus,  206,  219 
Cepheus,  219,  252,  257 
Ceres,  100,  102,  133 
Cerulli,  V.,  90 
Ceti,  Miri,  199,  257 
Cetus,  199,  225,  257 
Chacornac,  101 
Chaillu,  P.  du,  31,  32 
Chambers,  G.  F.,  78, 102, 137,  139, 

144,  153 
Charlois,  102 

Chromosphere,  the,  56,  58 
Clairant,  135 
Clerke,  Miss  A.  M.,  85,  125,  137, 

144,  147,  193,  265,  317 
Coggia,  146 

Coggia's  Comet,  146,  149,  151 
Coleridge,  38 
Columbus,  171,  172,  275 
Comets,  132-158,  281,  303,  316 
Comstock,  G.,  39 
Copeland,  E.,  152 
Copernicus,  N.,  22,  23,  24,  69,  77, 

185,  186,  275-278,  283,  284, 

285,  290,  305 

Corona  Borealis,  185,  195,  257 
Corona,  Solar,  58,  175,  176,  177 
Crabtree,  W.,  180 
Cygni,  Beta,  201,  203 
Cygni  (61),  185, 187,  188, 189,  210, 

258 
Cygnus,  185,   196,  219,  221,  252, 

253,  255,  256 
Cysat,  214 


Damoiseau,  135 

D'Arrest,  H.  L.,  127 

Darwin,  Sir  G.  H.,  228,  240,  241, 

242,  243 

Dawes,  W.  R.,  85 
Daylight  Comet,  148,  149 
De  Chesaux's  Comet,  142 
Deneb,  221 

Denning,  W.  F.,  108,  167 
Di  Vico,  F. ,  79,  140 
Di  Vico's  Comet,  139 


Dolmage,  C.,  188 

Donati,  G.  B.,  143,  152 

Donati's  Comet,  134, 143, 144, 145, 

151 

Doppler,  C.,  199 
Doppler's  Principle,  200,  212 
Douglass,  A.  E. ,  87 
Draco,  258,  305 
Dreyer,  J.  L.  E. ,  278 
Dyson,  F.  W.,209 

E 

Earth,  the,  17-25,  26-36,  37,  60- 
68,  70,  71,  75,  78,  82,  83,  84, 
96,  98,  104, 109,  110,  111,  120, 
132,  145,  155,  156,  157,  159, 
164,  166,  169,  170,  180,  189, 
190,  210,  211,  212,  217,  218, 
221,  227,  228,  230-235,  236, 
237,  240-244,  245,  247,  248, 
249,  274,  276,  277,  281,  285, 
287,  298,  306,  307,  319,  320, 
321,  322,  323 

Earth-Moon  system,  321,  323 

Eclipses,  lunar,  170,  171,  172 

Eclipses,  solar,  173-179,  309,  310, 
311 

Edinburgh  Observatory,  271 

Elger,  T.  G.,  43 

Encke,  J.  F.,  127,  128,  136,  137 

Encke's  Comet,  136,  137,  138,  316 

Eridanus,  258 

Eros,  103 

Eudoxus,  21 

F 

Fabricius,  J.,  198 

Faculae,  solar,  54 

Faye,H.,138 

Ferguson,  J.,  226, 304,  308-311,  314 

Flammarion,  C.,  37,  63,  94,  106, 

159,  205,  212,  213,  250,  323, 

325,  326 

Flamsteed,  J.,  124,  300,  301,  303 
Fomalhaut,  259 
Fontana,  293 
Fraunhofer,  J.,  55 
Frost,  E.  B.,  149 


G 

Galaxies,  external,  224,  225 


329 


INDEX 


Galaxy  (or  Milky  Way),  167,  193, 

219-225,  247,  250,  258,  285, 

325 
Galileo,  23,  52,  77,  106,  107,  111, 

114,  116,  117,  195,  214,  219, 

239,   261,   262,  283-288,  290, 

291,  293,  296 
Galle,  J.  G.,  127 
Gambart,  154 
Gemini,  123,  219,  255,  258 
Genesis,  Book  of,  230,  232 
Gill,  Sir  D.,  146,  190,  272 
Goldschmidt,  H.,  101 
Goodricke,  J.,  199 
Gore,  J.  E.,  74,  190,  197,  207,  223, 

224,  225,  247,  254 
Gravitation,  law  of,  24,  68,   125, 

295,  297,  303 
Green,  N.,  94 
Greenwich  Observatory,  126,  270, 

271,  303 

Gregory,  J.,  263 
Gregory,  R.  A.,  49,  57,  65,  172 
Guillemin,  119 

H 

Hale,  G.  E. ,  269 

Hall,  A.,  95,  260 

Hall,  M.,  130 

Halley,  E.,  133,  134, 135,  209,  298, 
299,  300-304,  305 

Halley's  Comet,  134,  135,  136, 139, 
141,  148,  303 

Harding,  101 

Harvard  Observatory,  269,  272 

Hebe,  101 

Hencke,  101 

Henderson,  T.,  187,  271,  272,  317 

Hercules,  206,  211,  255,  258 

Herculis,  Lambda,  211 

Herschel,  Caroline,  136,  313,  314, 
315,  316,  317 

Herschel,  Sir  J.,  136,  145,  202,  215 

Herschel,  Sir  W.,  24,  85,  123,  124, 
125,  129,  133,  142,  185,  201, 
202,  210,  211,  215,  216,  220, 
222,  224,  227,  228,  257,  263, 
264,  297,  311,  312-317 

Hesiod,  182 

Hevelius,  297,  301,  302 

Hind,  J.  E.,  101,  195 


Hipparchus,  21,  194,  273,  274,  275, 

300 

Holland,  Sir  H.,  127 
Holmes,  E.,  138 
Holmes'  Comet,  138 
Homer,  182 
Hook,  298 

Horrocks,  J.,  179,  180 
Howe,  H.  A.,  165 
Huggins,  Sir  W.,  152,  191,   192, 

195,  203,  212,  216,  318 
Humboldt,  160 
Huyghens,   C.,  84,  85,  117,  121, 

214,  262,  286,  292,  293,  294, 

296,  297,  298 

Hyades,  the,  205,  206,  260 
Hydra,  258 


Innes,  R,  148 


Janssen,  P.  J.  C.,  175 

Joachim,  279 

Job,  19,  76,  182,  206 

Juno,  101,  104 

Jupiter,  20,  21,  23,  60-68,  84,  93, 
98,  99,  100, 102, 106-114,  115, 
120,  134,  139,  140,  169,  181, 
186,  195,  233,  234,  246,  254, 
2<>0,  262,  267,  274,  285,  289, 
291,  292,  297,  304,  310,  322 

K 

Kant,  I.,  226 
Kapteyn,  J.  C.,  223 
Keeler,  J.  E.,  216,  218,  268 
Kepler,  J.,  23,  98,  134,  157,   179, 
194,  197,  235,  239,  261,  282, 
283,  284,  288-292,  295,  298 
Kirchhoff,  G.  R.,  54,  216 
Klinkerfues,  155 


Laplace,  P.  S.,  166,  227,  228,  245 
Lassell,  W.,  129,  130 
Le  Monnier,  124 
Leo,  160,  161,  184,  212,  255,  258 
Leonid  meteors,  160,  161,  162 
Le  Verrier,  U.  J.  J.,  126,  127,  128, 
129,  317 


330 


INDEX 


Lexell,  140 

Lexell's  Comet,  139,  140 

Libration,  41,  74,  80 

Lick,  J.,  266,  267 

Lick  Observatory,  113,  138,  173, 

216,  267,  269 
Light,  motion  of,  246-250,  306, 

323 
Lockyer,  Sir  J.  N.,  166,  175 

LoweilUprof.,73,  84,  86,  87,  88, 
89,  90,  91,  92,  93,  94,  95,  230, 
231,  232,  233,  269 

Lowell  Observatory,  87,  129,  269 

Luther,  R.,  101 

Lyra,  184,  211,  253,  259,  307 

Lyrse,  Beta,  200 

Lyne,  Delta,  211,212 


Maclaurin,  C. ,  314 
Madler,  J.  H.,  44,  85,  213 
Magellanic  Clouds,  207 


,21,  23,  6(^8,  80  83^97, 
98  99,  100,  103, 104, 109,  llo, 
169  181,  186,  195,  23  t,  254, 
274  277,  286,  289,  290,  291, 
292^  293,  304,  322 

Mastlin   M.,283,  288 

5^^.^34,86,9092,157, 

158,  251,  255,  256,  258 
Mechain,  136 

"'  20  21%3,  60-68, 69-75, 
TG  77,  78,  79,  80,  82,  84.  115, 
192  179,  180,  189,  254,  2.4, 
277,  289,  305,  322 

Messier,  C.,  140 

Metcalfe,  J.  H.,  102 

Meteors,  155,  159-167 

Midnight  Sun,  31,  32 

Milan  Observatory,  272 

Milton,  219 

Mirfak,  259 

Mizar,  201,  203,  260 

Moon,  the,  19,  21,  37-47,  70  73 
77,  82,  84,  145,  169,  170,  1-1 
172  173,  210,  228,  230,  23o 
236  237  239-244,  246,  260 
261  262,  274,  281,  285,  298 

331 


307,  309,  312,  320,  321,  323, 

325 

klorehouse,  152 
rtorehouse's  Comet,  152,  153 

N 

Nasmyth,  J.,  78 

Nebulfe,  214,  215,  216,  217,  218, 

223,  293,  316 
Nebular  hypothesis,  226,  227,  228, 

229 
Neptune,   60-68,    110,   123,   128, 

130,  131,  136,  143,  163,  188, 

189,  202,  234,  322 
Newcomb,  S.,  90,  267,  318 
Newton,   Sir  I.,  23,  24,  54,  133, 

202,  239,  263,  29v,  295-300, 

303,  304,  306,  307,  308,  310, 

312,  316 
Newton,  H.  A.,  160,  161 
Nice  Observatory,  87 
Nicetas,  276 
Nichol,  J.  P.,  206 

O 

Olbers,  H.,  100,  101,  151,  292,  317 
Gibers'  Comet,  139 
Ophiuchus,  195,  259 
Orion   183,  190,  208,  214,  215,  221, 

222,  255,  259,  285 
Orion,  nebula  in,  214,  215,  217, 

218,  229 


Palisa,  J.,  101 

Pallas,  100,  104 

Paris  Observatory,  138,  154,  2<0 

Peck,  W.,  196,  200,  254 

Pegasus,  216,  259 

Perrine,  C.  D.,  113,  177,  217 

Perrine's  Comet,  148 

Perseid  meteors,  162 

Perseus,  185,  197,  213,  219,  247, 

255,  259 
Peters,  101 
Philolaus,  276 
Photosphere,  the,  52,  58 

Piazzi,  G.,  99,  292 
Pickering,E.C     197   203,2/0 

Pickering,  W.  H.,  44,  4o,  b7,  88, 
89,  122,  131,  177,  242,  243 


INDEX 


Pisces,  259 

Pleiades,  the,  182,  205,  206,  213, 

221,  222,  260,  285 
Plough,  the,    183,   184,  201,  208, 

213,  252,  253,  255,  257 
Pole  Star,  the,  183,  192,  249,  255, 

260,  307 
Pollux,  192,  258 
Pons,  J.  L.,  136 
Pens'  Comet,  139 
Pontecoulant,  135 
Potsdam  Observatory,  271 
Pound,  J.,  304,  305 
Praesepe,  206,  256,  288 
Proctor,  R.  A.,  58,  85,  86,  88,  89, 

94,  203,  204,  223 
Procyon,  192,  202,  257 
Prominences,  solar,  56,  175,  176 
Ptolemy,  21,  22,  274,  275,  276,  284 
Pulkowa  Observatory,  271 
Pythagoras,  76,  275 


R 

Regulus,  192,  212,  258 

Ricco,  A.,  108 

Rigel,  190,  192,  193,  259 

Rings  of  Saturn,    116,    117,   118, 

119 

Ring  nebula,  216 
Roberts,  I.,  220 
Roemer,  246,  306 
Rosenberger,  135 
Rosse,  Earl  of,  216,  220,  264,  265, 

267,  269,  297 


S 

Sagittarius,  219,  260 

Satellites,  of  Mars,  95,  96 ;  of 
Jupiter,  111,  112,  113,  114, 
285,  291,  297,  304,  310;  of 
Saturn,  121,  122  ;  of  Uranus, 
129,  130;  of  Neptune,  130 

Saturn,  20,  21,  23,  60-68,  93,  99, 
110,  115-122,  123,  124,  169, 
195,  234,  254,  264,  274,  289, 
293,  322 

Scheiner,  C.,  52 

Schiaparelli,  G.  V.,  48,  72,  73,  79, 
80,  81,  86,  89,  92,  93,  94,  163, 
164,  166,223,272,318,319 


Schmidt,  J.  F.  J.,  44,  195,  196 

Schroter,  J.  H.,  71,  72,  79,  80,  81 

Schwabe,  S.  H.,  53 

Scorpio,  184,  203,  219,  255 

Secchi,  A.,  85,  191,  192,  272,  318 

Seeliger,  H.,  198,  205 

Serviss,  G.  P.t  188,  189 

Sidereal  day,  35,  36 

Sime,  J.,  316,  317 

Sirius,  84,  185,  186,  192,  193,  198, 
202,  248,  256,  257 

Smyth,  Admiral,  257 

Solar  day,  35,  36 

Spectroscope,  the,  54,  55,  56,  152, 
191,  192,  193,  199,  200 

Spica,  203,  210 

Star-clusters,  206,  207,  316 

Star-drift,  213 

Stars,  dark,  203 

distance  of,  186-190,  305 

—  distribution  of,  222,  223 

double,  201-205 

—  proper  motions  of,  208-212 

temporary,  194-198,  280 

variable,  198,  199,  200 

Stellar   Universe,   the,   222,   223, 
227 

Struve,  F.  G.  W.,  187,  202,  272, 
317 

Struve,  0.,  129,  202,  272 

Sun,  the,  18,  19,  26-36,  37,  46,  48- 
59,  60-68,  72,  73,  74,  78,  79, 
83,  120,  122,  132,  137,  141, 
150,  151,  159,  167,  169,  170, 
172-179,  180,  188,  189,  190, 
191,  193,  210,  211,  213,  221, 
227,  228,  231,  233,  234,  236, 
237,  239,  241,  243,  245,  246, 
274,  277,  285,  286,  304,  30!), 
310,  311,  312,  322,  323 
Sun-spots,  51,  52,  53,  54,  286,  311 


Tacchini,  P.,  57,  175,  176,  272 

Taurus,  185,  255,  260 

Telescopes,  reflecting,  263,  264, 
265,  269,  296,  297,  314;  re- 
fracting, 262,  263,  266,  267, 
268,  285,  293 

Temperature  of  sun,  50 

Tennyson,  207 


332 


INDEX 


Tidal  friction,  240-244 
Tides,  the,  236-244 
Todd,  D.  P.,  35,  36 
Todd,  Mrs.  D.  P.,  177 
Transits  of  Venus,  179,  180,  303, 
311  ;  of  Mercury,  180,  181,  305 
Trouvelot,  81 
Turner,  H.  H.,  103 

U 

Ulugh  Beg,  274,  275 

Uranus,  60-68,  99,  110,  123,  124, 

125,  126,  127,  129,  130,  133, 

234,  315,  322 

Ursa  Major,  183,  203,  209,  260 
Ursa  Minor,  183,  260,  207 


Vega,  185,  186,  192,  193,  253,  307 
Venus,  20,  21,  23,  60-67,  76-82, 
83,  89,  106,  115, 145, 169,  179, 
180,  186,  189,  194,  195,  234, 
254,  260,  274,  277,  285,  289, 
297,  303,  305,  311,  322 


Vesta,  101,  104 
Virgo,  184,  187,  255,  260 
Vogel,    192,   199,   200,    212,   271, 
318 

W 

Washington  Observatory,  95 

Wells'  Comet,  152 

Wilson,  H.  C.,  152 

Witt,  103 

Wolf,  Max,  102, 136,  138,  215,  220, 

272 

Wordsworth,  219 
Wren,  298 


Yerkes,  C.,  268 
Yerkes  Observatory,  149,  268 
Young,  C.  A.,  50,  56, 129,  175, 176, 
177 


Zach,  F.  X.,  99 
Zodiacal  light,  167 


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THIS  BOOK  IS  DUE  ON  THE  LAST  DATE 
STAMPED  BELOW 


AN     INITIAL    FINE     OF     25     CENTS 

WILL  BE  ASSESSED  FOR  FAILURE  TO  RETURN 
THIS  BOOK  ON  THE  DATE  DUE.  THE  PENALTY 
WILL  INCREASE  TO  SO  CENTS  ON  THE  FOURTH 
DAY  AND  TO  Sl.OO  ON  THE  SEVENTH  DAY 
OVERDUE. 


S£P  28  J932 

FEB  12  1933 

A*    I31934 

MOV  16  1931 

MAY   19  ig 

OCT    2    343 


;  v;- 

APRS    1954  LU 


LD  21-50m-8,<32 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 


